microwave water experiment

Microwaved Water -- See What It Does to Plants

Does an experiment prove water that has been heated in a microwave oven is harmful to plants, david mikkelson, published aug. 8, 2006.

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The introductions of new, widely-adopted technologies are often accompanied by fears of possible deleterious effects from the use of such devices, everything from concerns that telephones would spell the end of regional accents to parental admonitions not to sit too close to the television (lest you ruin your eyes!). Usually these fears are largely allayed after a few years, as the technologies improve and become ubiquitous, and evidence of the feared negative effects fails to materialize. Nonetheless, even though the microwave oven has been a standard household appliance for several decades now, rumors continue to linger that microwaves somehow "change the molecular structure" of consumables and therefore make food products heated in them unsafe to eat. The sample "experiment" represented below is an expression of that sort of rumor, but it is pure junk science, both in its methodology and its conclusions:

Microwaved Water - See What It Does To Plants Below is a science fair project that my granddaughter did for 2006. In it she took filered water and divided it into two parts.. The first part she heated to boiling in a pan on the stove, and the second part she heated to boiling in a microwave. Then after cooling she used the water to water two identical plants to see if there would be any difference in the growth between the normal boiled water and the water boiled in a microwave. She was thinking that the structure or energy of the water may be compromised by microwave. As it turned out, even she was amazed at the difference. I have known for years that the problem with microwaved anything is not the radiation people used to worry about, It's how it corrupts the DNA in the food so the body can not recognize it. So the body wraps it in fat cells to protect itself from the dead food or it eliminates it fast.. Think of all the Mothers heating up milk in these "Safe" appliances. What about the nurse in Canada that warmed up blood for a transfusion patient and accidently killed them when the blood went in dead. But the makers say it's safe.. Never mind then, keep using them. Ask your Doctor I am sure they will say it's safe too. Proof is in the pictures of living plants dying. Remember You are also Living. Take Care.

First of all, there's some doubt as to whether the photographs displayed above actually depict a real experiment rather than some digital fakery, as the "Day One" and "Day Five" photos appear to be remarkably consistent in camera angle, lighting, positioning, background elements, and everything else save for the appearance of the "dying" plant:

Regardless, water heated in a microwave oven is no different in "structure or energy" than water heated with a gas flame, on an electric stove, or over a wood fire: It's just water, plain and simple. More important, though, is the awareness that drawing valid scientific conclusions from experimentation involves conducting multiple trials under carefully controlled conditions, something not in evidence here. The extraneous factors that could have produced the exhibited results (i.e., one live plant and one dead plant) exhibited above are legion. For example:

• One plant could have been compromised from the very beginning and would have died even if both plants were treated alike.
• The container used to store or boil the microwaved water could have introduced a residual substance into the water that hindered plant growth.
• The soil or bedding material used for one of the plants might have contained something (either originally or introduced later) that hindered plant growth.
• The two containers of water might have been heated and/or cooled unequally, resulting in one plant's receiving warmer water than the other.
• The plants might have been subject to differing environmental factors (e.g., light, heat) due to their placement, or affected differently by external factors (e.g., insects, pets).
• Since the experiment was not conducted "blindly," the possibility that the experimenter in some way influenced the results cannot be ruled out.

Rather than simply speculate, though, we performed the same experiment in a more controlled manner. We started out with three each of three different types of plants: one member of each set was given water that had been boiled on a gas stove, water that had been boiled in a microwave oven, or water that had not been boiled at all. All the water used in the experiment came from the same source, the same vessel was used for boiling water both on the stove and in the microwave, and all three types of water were stored in identical containers. The water given to all of the plants was at room temperature. The plants were kept in a carefully controlled environment that protected them from our pets and equalized (as much as possible) their exposure to environmental factors and watered in the manner described above for a period of time identical to that of the original experiment.

As evidenced by the photos below (taken while the plants were briefly removed from the environment in which they were tended and placed in a setting better suited to photography), at the end of that time period all three plants in each set were fairly thriving. When a non-participating observer was asked to indicate (blindly) which plant in each set he thought had fared the best, in two cases he selected plants that had been given microwave-boiled water, and in one case he selected a plant that had been given unboiled water:

As for the coda to the example quoted at the head of this page, there have been some cases in which the use of microwave-heated blood in medical procedures has been cited as causing serious problems, but not because microwave heating "corrupts the DNA." Rather, conventional microwave ovens can heat blood too quickly and/or too unevenly (resulting in hemolysis ), so standard (and slower) blood warming procedures are generally preferred or mandated.

By David Mikkelson

David Mikkelson founded the site now known as snopes.com back in 1994.

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What happens to plants when given microwaved water? (Is it time to ditch the microwave?)

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I grew up using a microwave on a daily basis. Half of what I ate in high school was something I took out of the freezer and popped into the microwave.

As an adult, I began cooking my own food, but I continued to rely on a microwave to re-heat the food for a second or third meal.

Not too long ago, I started hearing some things about how using a microwave isn’t good for you.

As a scientist, I wanted to put this to the test to see for myself.

So I purchased two plants and decided to water one plant with water that had been heated to boiling on the stove and another plant that had been heated to boiling in the microwave. In both cases, I let the water cool down to room temperature before giving it to the plants.

Note: Find more science experiments on my Science Activities for Kids page!

The two plants I used were purchased at the same time from our local hardware store. Both plants were approximately the same size and had a similar number of purple blooms on them. Both plants sat right next to each other in a sunny spot on our front porch.

I watered the plants almost every day (the almost will become relevant later in this post), always with the same amount water. The only difference is that one plant received water that had been heating to boiling on a stove (i.e. “stove-boiled water”) and one received water than had been microwaved to boiling (i.e., “microwave-boiled water”). Note that I always let the water cool down to room temperature before giving it to the plants.

After 11 days, there was already a very big difference in the health of the plants.

While the plant provided with stove-boiled water grew and thrived, the plant given microwave-boiled water had turned very dry and lacked the beautiful purple blooms of the other plant.

So it looked like giving the plant microwave-boiled water had definitely lead to its demise, but I wanted to run the experiment again to see if I would get similar results.

I purchased two more plants, this time Calibrachoa plants with yellow flowers. As before, the plants sat together on our sunny front porch and I watered them every day with equal amounts of water.

This continued for about three weeks, and I got discouraged as the plants were both thriving and doing well. I thought maybe the results from the first experiment had been a fluke.

Then after diligently watering the plants every day, there was one really hot day that I forgot to water them.

I went out the next morning and found that both were wilting from the hot temperatures. But it was also clear the the plant given stove-boiled water had fared much better than the plant given microwave-boiled water.

Looking back, I realized there were days during the first experiment with the purple flowered plants when I had forgotten to water them as well, which may have contributed to the quick differences I saw in their overall health. I was so diligent about watering the plants on a daily basis the second time that it obscured the developing health issues that were occurring in the microwave-boiled water plant.

What I concluded from this experiment is that both stove-boiled and microwave-boiled water would help the plants do well under optimal conditions. But as soon as the plants were stressed (such as from a hot day with no water), the plants given microwave-boiled water proved to be much more vulnerable than the plants given stove-boiled water.

This experiment has convinced our family of the need to give up our microwave. Something about using a microwave is changing the water in a way that does not promote optimal health and vitality.

What do you think?

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Reader interactions, 15 comments.

September 18, 2018 at 4:10 pm

Thank you for doing this experiment pertaining to “the microwave.” I too was a microwaver since my teens and can relate to you on this.. For the last four years we have not used a microwave, since we feel that it isn’t healthy to use. My two sons (1 yr and a 3 yr old) have never experienced having anything microwaved. You now have encouraged me to perform this experiment and when I complete it, I will let you know the results.

September 18, 2018 at 4:37 pm

Yes, please do let me know what your results are!

October 22, 2018 at 5:33 am

This is an eye opener. My microwave is out of order and I’m not going to fix it. The radiation is not good for our health. Although it seems to be an easy option, with a little effort of alternative cooking and reheating methods, we can take care of our health.

October 22, 2018 at 10:24 am

It was hard for me at first to give up the microwave because it was such a quick and convenient option. But now we have new routines and I don’t even think about the microwave anymore.

November 2, 2018 at 7:09 pm

Does it have similar affect if we use induction cookware.

November 3, 2018 at 3:48 am

I have no idea but it would make for an interesting experiment you could do!

November 3, 2018 at 3:24 am

Weird, I’d always suspected microwaving (and other EMFs in general, including the incoming hordes of 5G antennas) weren’t good for health. But I saw a video where Neil deGrasse Tyson was saying that all the microwaves do is cause the water molecules to vibrate enough just so heat is created, so really it was just like friction producing heat and nothing to worry about. I’d be really interested to see some large-scale attempts at reproducing this experiment. Anyway, thank you for this awesome website–it’s made for a lot of fun afternoons with my nephew!

January 16, 2019 at 12:24 am

Jon, if there is one thing you can be sure of is that you cannot trust anything Neil DeGrasse Tyson says.

He is an misinformation actor. Not a real scientist.

March 3, 2022 at 11:32 am

get an emf reader and hold it to your cup of water after you heat it in the microwave…. It’s insane how much radiation is in your water and we drink that. <3

July 7, 2019 at 12:18 pm

Curious….One question that came to mind while reading this was: what did you heat up the water in when using the microwave? A plastic or glass container?

July 7, 2019 at 8:28 pm

I microwaved the water in a glass.

March 13, 2021 at 10:35 am

Mini years ago I told one of my sons about this so he decided to try in the same experiment by germinating seeds for his school science project. None of the seeds given the previously heated microwave water germinated.

September 9, 2019 at 5:07 pm

So I am doing this experiment for my Science Fair Project! I will be doing a fresh watered plant, 1 minute microwaved water plant, and a 5 minute microwaved water plant. My questions is how much water did you feed your plants? I have some mums so it might be different.

September 23, 2019 at 12:32 pm

The exact amount of water I gave my plants is less important than the fact that both plants got the same amount. You may need to adjust the amount of water you give depending on how thirsty your plant is. For example, on hotter days my plants would dry out faster so I would give more water. On cooler days I could give less water. As long as you give both plants the same amount of water, you will maintain an appropriate control.

I am glad you are doing this for your science experiment. Be sure to note my conclusion that the plants both did equally well when given enough water, but the plant receiving boiled water did much better when the plants were stressed.

Of course I cannot say if you will get similar results, but if your plants all seem to be growing the same you may need to stress them out to see a difference.

April 22, 2022 at 8:29 pm

I saw this experiment done by someone in a healthy living capacity. It has always stuck with me and today, years later, I remembered to google it. Your video came up and addressed all the points! I was anti microwave for a very long time and have started using one at work. No more! Bad enough I sleep near my cell phone and wear my apple watch, I think it is wise to be cautious how much radiation we are exposed to. Thank you for putting this experiment out there!

Microwave Water Plant Experiment – Science Fair Project

• May 28, 2022
• 7-9 Year Olds , Biology

In this experiment, we are going to measure the impact of using microwave water on plants .

Using this experiment let’s see :

• How plants react to microwaved water.
• How different liquids affect its growth.
• Kids can learn about plants’ health.

Let us explore some plant science today and have fun.

Impact of Microwaved Water on Plants

A plant fades away when it receives microwave-heated water every day. i.e. Microwaved water

Let us see how the hypothesis works out.

Things required to perform the Experiment

Our experiment requires materials that are easily available in-home:

• Any kind of plants for experimenting

Preparations

• Arrange your experimental table on your balcony or any open place.
• Arrange the fresh plants from the garden on the experiment table neatly in a row.

Primarily arrange all this so that plants do not fade away or get dry due to other reasons apart from our experiment supplies.

Instructions for the experiment

• Take the required amount of water for experimenting the plants.
• Make sure the water is not contaminated with any other substances or chemicals because the contaminants may change the result.
• Each serve it’s necessary  to pour one or two mugs of water for each plants.

Step 2: Heat the water using Microwaves

• Take required amount of water in a glass bowl and keep it inside the microwave for heating. Switch on the microwave power plug.
• Set the time for heating according to the microwave capabilities.
• Once the process of heating the water , take out the glass bowl which is very hot using heat proof microwave gloves.

Tip: Please maintain the quantity of water to heat according to the microwave capacity measurement.

Step 3: Watering Plants

• Now Pour one or two mugs of microwave  heated water to the plants every day without fail by following the step 1 and 2.
• Remember quantity of  water depends on the plant size  taken for the experiment.

Take two more plants for experiment using rice water and normal tap water. Let’s check how plants react to different liquids.

• Already experiment plant number 1 with microwave water.
• Now start experimenting other two plants with rice water and normal tap water  respectively.

Note : Rice water is obtained from the soaked rice before cooking the rice. Also obtain the rice water by washing the rice. Everyday feed these water to the plants according to the label along with the microwave heated water.

If season supports, let’s also experiment plants with the rain water.

Observation and results

• Plants shows difference in their health after receiving  different types of water for few days.
• Plant that are poured with microwave heated water fades away slowly whereas the plants with rice water, rain water and normal tap water grows healthily.

On seeing faded plants seems disappointing, but here is the science behind this experiment. Microwave heated water is harmful for the plants life .

Is there any reason or little science that could explain our observations and results in our experiment!?

Yes, there are clear cut reasons for why some plants faded away whereas others grew up nicely.

Let’s see how the microwave heated water affect the plants blooms:

• The treatment of water by microwaves causes drastic changes in conductivity, pH  and mobility of water molecules.
• Microwaves also has the ability to produce changes in absorbency of the plant cell membrane.  
• In addition, it also inhibits plant cell growth rate, interacts with the ions and organic molecules.
• The main culprit behind all these consequences by the microwaves is the radiation . The effect of radiation makes the plant lost its blossom and finally fades away.

Following are the observation noted with this experiment:

• Plants that are experimented with salt water does not allow the plant roots for osmosis which happens through the plant tissue. As a result the salt draws water out of the plant, dehydrates and eventually kills. Thus, the plant fades away when given with salt water.
• Plants that are experimented with rice water and tap water shows positive results. Compared to tap water, plants treated with rice water shows good growth.
• This is because rice water works as effective as NPK fertilizer to promote a healthy and surprising plant growth in terms of number of leaves and higher biomass.
• Rice water make all this happen by supplying essential nutrients of sodium and potassium which are very much essential  to a plant.
• Lesser growth  of the plants that are treated with tap water is mainly due to high concentration with the salts of magnesium and calcium which are not good for plants growth. These concentrated salts cause the plant dehydrate as they take out water from the root structures. Hence, there is slower growth rate in plants treated with tap water.
• Rain water and bottled spring water are great at amazing growth rate in plants.
• The sugar and salt water actually hurts plant growth.
• Distilled and tap water may not hurt the plant growth but the growth rate may decrease when compare to rain and spring water.  

Safety: As using electronic equipment  like microwave, kids need to be very careful. It is better to ask for adult help while dealing with microwave. Be sure to use heat proof microwave gloves to avoid unnecessary burns caused by the superheated equipment. However, adult supervision is mandatory.

Microwaves make things hot. It heats the water beyond the actual boiling point of water by passing tiny waves into the water at random locations causing the molecules of water vibrate. Eventually makes the water molecules spin around two opposite poles (referred as dipole ) rapidly. This all happens just because of the radiation which imparts energy to the water molecules to move back and forth exactly at the frequency of microwaves.

It is not safe to microwave water. It is always a bit safe to boil water in a plate when using microwave. Because the hottest point is located at the bottom of the plate whereas in case of glass the hottest point is located in the water. Glass does not get heated much i.e. at least not much and radiates some heat energy to the surroundings. This is the reason heating water in a glass when using microwave is not safe.

Yes, absolutely! If you want to purify water, heat it in microwave long enough to eliminate gems and microorganisms. Microwaves don’t kill bacteria directly, instead generates heat that kills bacteria present in the water.  Microwaves are great time-saver and kill bacteria when water is heated at safe internal temperature.

Microwave was invented by an American Engineer Percy Spencer. He invited modern microwave after World War II by using a technology that is developed during the war called ‘Radar Technology’ . It was first sold in 1946. In the beginning, people were scared of using it because of the radiation it emits and the other concerns were too big in size and expensive. Eventually, the fears faded away since the technology improved.

Boiled water can also be used to kill weeds and prevent plant diseases around the garden. In fact, treating plants with hot water works effectively and sounds like one of the best and crazy home-made remedies. Gardeners generally boil water if they believe it contains chemicals or impurities that may be dangerous to the plant health. Theoretically, hot or boiling water kills most contaminants and makes the water safer for plants. But the boiled water must be cooled and bring to the room temperature before watering to plants.

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The Difference Between Boiling Water And Microwaving It

While we'd all love to have time to wait for the water in a tea kettle to boil whenever we want to make a cup of tea, sometimes we just don't get that luxury. If you need hot water right away in the morning, it's much easier and quicker to turn to the microwave. But are the results really the same? You can, of course, nuke a mug of water in the microwave, and it will emerge steaming hot. 

But if you're expecting the exact same results as the ones that come from using a kettle, you may be disappointed. According to a 2020 study published in  AIP Advances , liquids warmed in the microwave will end up hotter on the top than on the bottom. The researchers conducted an experiment showing that the temperature difference between the top and bottom of a glass of water heated in the microwave was a whopping 7.8 degrees Celsius (14.04 degrees Fahrenheit) in some places. 

When you use a tea kettle or boil water on the stove, however, you'll end up with a liquid that's been heated much more evenly. This is because the water will have been warmed from the bottom, which causes it to naturally rise and increase the temperature of the surface liquid, leading to hot water throughout your kettle or pot instead of a mug with noticeable hot and cold spots.

How to help water heat evenly in the microwave

So, if you're short on time and need to stick your mug in the microwave, are you doomed to drink unevenly heated tea? Not necessarily. While it's true that nuking your water won't yield the same uniform results as boiling it, there are a few things you can do to help things along. As with microwaved food, make sure to stir your water after it comes out of the device before inserting your tea bag, which will help the warm, surface-level liquid heat up the cooler parts underneath. 

You can also get ahead of the uneven temperatures and take your mug out of the microwave at short intervals, stirring in between each one. If your device has a turntable, you're in luck — simply place your cup on its edge so it doesn't get stuck in a cold spot. There are also special microwave-safe, silver-rimmed cups available that can help heat liquids more evenly.  

To avoid super-heating, which occurs when the temperature of the water surpasses boiling point and causes an eruption in your microwave , you can also heat your water with a wooden spoon or toothpick in the mug. The wood item helps the bubbles dissipate, encouraging the water to boil instead of overheating. It takes a little finessing, but it is possible to get adequate hot water from the microwave. Still, if you have the time, boiling it on the stove is a much more ideal option.

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Is microwaved water harmful to plants?

Catherine Stewart

Can watering plants with water that’s been microwave-boiled, then cooled, kill them?  I was recently alerted to this silly myth doing the rounds on the internet when explaining to a young acquaintance why I prefer to microwave-cook my vegies. So it seems it’s still duping people with its apparent ‘scientific’ evidence, so here’s a bit of my own debunking.

The alleged ‘science fair experiment’ by ‘Arielle Reynolds’ (variously from Knoxville TN, or Sussex UK) in 2006:

“Below is a science fair project that my granddaughter did for 2006. In it she took filered water and divided it into two parts.. The first part she heated to boiling in a pan on the stove, and the second part she heated to boiling in a microwave. Then after cooling she used the water to water two identical plants to see if there would be any difference in the growth between the normal boiled water and the water boiled in a microwave. She was thinking that the structure or energy of the water may be compromised by microwave. As it turned out, even she was amazed at the difference.”

Snopes**, that great internet myth debunking site, has had a good look at the photo of the microwave-boiled watered plant on the left from Day 1 to Day 5 of watering, and showed how the photo has been manipulated (and the leaves probably removed with scissors). See the Snopes mock-up here .

BUT what nobody else seems to have noticed is perhaps only obvious to a gardener…..

1. How do you water a plant without moving one speck of perlite on the surface of the potting mix? If you look at Days 1 to 5, you’ll see that every single bit of that very lightweight substance is in exactly the same place.

2. How does a dying plant wilt so unevenly? Notice that the longer leaves on the right are exactly the same – robust and turgid – from Days1 to 5, but the others mysteriously change.

3. Where are the leaves that supposedly died? And how do each of the leaf stems end up with a neat, flat cut line at their extremity? Wouldn’t they also be withered?

It’s disturbing to see such rubbish still convincing so many people, if only for their inability to identify the essential elements of a properly conducted scientific trial, all missing from this obvious fakery.

And yes, I will continue to enjoy my highly-nutritious, microwave-cooked vegies!

[**If you ever get an email telling you about some extraordinary or ‘dangerous’ fact, or how a girl dying in the UK needs a gazillion postcards from around the world, run it through the Snopes site first. Odds on you will find it is an internet/email hoax]

Replication is a fundamental principle of science, the ability to repeat an experiment and get the same answers. So let’s replicate this one.

Find 2 plants. Cut off the leaves of the one you like least. Blame something.

Thanks kiwi-ian, I needed a good belly laugh today!

G’day guys, I know that everyone has different thoughts on this topic and they all may be right in one way or another but I have done this experiment myself. I had 3 pots with 1 Bean plant in each, one plant given rain water, one given town water and the other given microwaved rain water. It did take a couple of days for any noticeable differences but 2 of the bigger leaves on the plant started to go yellow as if it was dying and it turned out it was, both of the leaves shrivelled up and fell off, there were roots starting to grow up on the stem of the plant up to probably half a cm above the soil and there were also a very minimal amount of roots on the plant to the other 2 plants. I did exactly the same experiment with cucumber plants and the microwaved water had exactly the same effect but I had 2 cucumber plants in each pot so I had 6 plants all up. If you think that this is a load of crap I don’t care but please by all means I will show you photos if you would like.

Cheers, Zac

Hi Zac – what you’re reporting is not crap but it’s not science either. Observations of something unusual or surprising happening is often how scientists start their more formal and rigorous investigations. But it’s not an experiment in the scientific sense unless you use correct scientific method, where you start with a hypothesis and design a carefully controlled experiment to test it and then use statistical analysis on the results to reach a conclusion. For this sort of experiment that means that you need a much larger sample size than just a few plants and you also need to control for all sorts of variables that might affect the results, like variations in seed or seedling quality, transplanting success, light, temperature, growing medium, plant hygiene and pests and diseases – there’s a very long list! Scientific method also requires replication ie you need to conduct exactly the same experiment many times over and get similar results to be sure that your first result was not unusual. For real scientists there’s yet another step – they have to submit their experiment for peer review, which means that other professional scientists around the world read the experiment report, and a majority of them must agree that the experiment has measured what it set out to do and the conclusions are based on good quality results and proper analysis. Only then will a scientific journal agree to publish the results and even then it might be later shown by other scientists to be poor science and not reliable evidence. So until you, or the others out there who worry about microwaved water, can conduct a proper scientific experiment and get reliable, repeatable and peer reviewed results, there cannot be any credible proof at all that microwaved water can harm plants.

Scientific tests ( properly done) showing alteration of the properties of water lasting a long time post microwave treatment . Interesting is the increase in hydrogen peroxide levels. http://www.hindawi.com/journals/aot/2017/5260912/

Hello David – while on the surface this published study looks ‘scientific’, I have serious doubts about the reputation of the journal in which it is published. Credible scientists would not publish a study about the effects of microwaving water in an Egyptian journal called ‘Advances in Optical Technologies’. This journal is defunct after only a few years of publishing, and this study has not been cited once or replicated by any other researcher since it was published 4 years ago. I’m confident that the rest of the scientific world does not accept the validity of its results any more than I do.

Thanks for this piece of humour with a serious side, Catherine. Not only do I agree with the points you make, but I am also a great fan of the Snopes site!

I suppose what vaguely interests me as well is why anyone would bother to mock up the experiment in the first place?!!

My guess is that it’s because some people are obsessed with trying to discredit things they don’t think are ‘natural’, like using microwaves for cooking. Because it’s based on belief not science, they can’t find any proper research that supports that belief, so they have to make it up instead. Obviously they don’t have similar issues with using computers!

BUT HOW DO SOME PEOPLE KNOW THAT MICROWAVE WATER HARMS PLANTS?????????????????????????IM SO FREAKED OUT I NEED ANSWERS FOR MY SCIENCE PROJECT

Nobody ‘knows’ that microwaved water harms plants. They’ve seen this so-called evidence on the internet and accepted it as truth without stopping to think about whether the experiment was either real, plausible or repeatable. Microwaved water has no harmful effect on plants. Go ahead and do your own proper experiments and you’ll find that microwaved water is exactly the same as any boiled water. Maybe you should do a science project on why people manufacture false evidence and publish it on the internet?

My son did this experiment partly to show the fake experiment (shown here) was….urm..fake ! However he now has a problem. He used a control (tap) however the purified water plant is doing really well, tap water one second and microwaved one in third. It is not dying, and does not look unhealthy – but there is a big difference now between the size (height and width) of the plant watered with purified water every day and the one watered with microwaved water (boiled and cooled) He just can’t find out why- and why I am googling to see if I can find out why !! He made sure all have same conditions, all were grown from seedlings and are the same age, and all have the same light and amount of water as the same time. The expt was supposed to show there is no difference, but there obviously is! Today he asked random people to say which they thought were the healthiest and all gave 1,2,3 in the same order (purified, tap, microwaved) – not knowing anything about the expt. Aaarrrgggh. So WHY is there is a difference? It’s not killed it but definitely stunted its growth.

Hi Emma – an important part of any scientific experiment is that it must have an appropriate sample size so you can control for other factors that might affect the outcome. A sample size of one plant per type of watering is not ‘scientific’ as it cannot exclude any other factors. The difference in the plants’ response is most likely due to natural seedling variance but it could also be any number of other factors, like subtle differences in the growing mix, or a fungus/insect etc in the growing mix, or insect attack on the plant (and you can’t always see insects with the naked eye that cause stunting, like thrips) or just poor watering of one seedling before you even bought it which would have damaged its developing root system. Try repeating the experiment with at least 10 plants per watering type before you reach any conclusions about which water type causes a different growth rate. I’ve bought punnets of seedlings of lots of different types of plants that I’ve planted in the garden or in pots and there’s always several that don’t grow nearly as well as the others.

Make sure you use a glass container for the microwave water as plastics leach harmful chemicals

Hi Jazz – although some plastics (Type 3) can leach phthalates, these are harmful to humans as they disrupt the endocrine system, which plants do not have. Plants are not harmed by microwaved water whether the container used for watering is plastic or glass.

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Science project, microwave plant experiment: radish seed germination.

The sprouting of seeds is called germination . A germinating seed has a baby plant, called an embryo , on its surface. This tiny living thing gets its nutrients from the cotyledon , which is the fleshy part of seed. The cotyledon may or may not be in two pieces. As the plant embryo matures, the downward growing part becomes the root system , whereas the upward growing part becomes the shoot system . The cotyledon sustains the baby plant until it bursts through the top of soil and starts using the sun to make its own food.

Germination is an intricate process, and many factors, including lack of water or strong chemicals, can prevent it. Microwaves also can affect the germination of seeds. The microwaves emitted by a microwave oven are a form of radiant energy that fats and water in particular absorb. This absorbed energy can warm up your food, but what effect would it have on a radish seed? Would microwaving a seed help or hinder its growth?

How do microwaves affect radish seed germination?

• Aluminum foil
• Paper towels
• Labels or masking tape
• Permanent marker
• Microwave oven
• Microwave safe coffee cup
• Radish seeds
• Another microwave safe container
• Spray bottle
• Box or drawer
• Using the ruler, cut out seven 20 cm x 16 cm rectangles of aluminum foil.
• Cut six rectangles of paper towel, 18 cm x 15 cm.
• Make the labels for your experiment on the paper towels: 0 seconds, 30 seconds, I minute, 2 minutes, 4 minutes, and 8 minutes.
• Make creases in the paper towel pieces by folding them into thirds, each 6 cm long.
• Set a paper towel in the middle of one piece of aluminum foil.
• Using the spray bottle, spray the paper towel until all of it is moist, but not dripping wet.
• Make a line of about 10 radish seeds down the center of the paper towel.
• Fold the foil around the paper towel. 
• Write “0 seconds” on a label and place it on the foil packet. This will be your control group.
• Fill the coffee cup with water and place it in microwave. This cup will absorb any excess energy caused by the microwaving of the seeds. Don’t forget this step!
• Put about 10 radish seeds into the dry microwave safe container. 
• Set the timer for 15 seconds, make sure you have both the radish cup and water cup inside, set the power to high, and hit start.
• After the seeds have been microwaved, remove them and place them on another paper towel bed and foil. Label with the 15 seconds label.
• Dump out the water in the cup and put in new cool water.
• Repeat the procedure microwaving radish seeds for 30 seconds, 1 minute, 2 minutes, 4 minutes, and 8 minutes. 
• Place the foil packets in a box or drawer.
• Check the 0 seconds packet for germination after two to three days. If no seeds have started sprouting, rewrap and check again every day until you see germination.
• You might need to spray the paper towel with more water if it’s dry.
• If the 0 seeds have started sprouting, check the other seeds. Record your results this data table:

• Keep observing the germinating plants for at least four more days.  Note any differences in how long it takes the seeds to germinate and root or shoot system growth.

Results will vary depending on the strength of your microwave oven and radish seeds. The radish seeds that weren’t microwaved at all should germinate in a couple days. The stem system with tiny leaves and the root system with tiny root hairs should become more and more evident. Seeds only microwaved 15 seconds might actually show more sprouting early on. Seeds microwaved for longer periods won’t sprout at all. If all your seeds sprout, you need to redo your experiment with higher microwave times, if none of them sprout, you need to redo the experiment with lower microwave times. Don’t be discouraged, real science is all about trial and error!

Seeds need a moist environment to sprout. Your control group of seeds that weren’t microwaved will show you how long sprouting takes under normal conditions. A possible explanation for why seeds microwaved a short time sprouted more than the control seeds is that the heating opened the seeds' coats a tiny bit, allowing water in and starting germination sooner. There are a couple reasons why the seeds microwaved for longer periods did not germinate at all. The water absorbed the microwaves so extensively that it caused the water in the seeds to boil away. A dried out seed can’t germinate even if water is added later. The microwave oven also could have damaged the essential fats the seed needs to grow.

Going Further

Try experimenting on different seeds. Are some seeds more sensitive to microwaves than others? What about their structure causes this variation? You might also try microwaving the soil.

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August 8, 2024

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Microbes conquer the next extreme environment: Your microwave

by Frontiers

Since the industrial revolution, microbes have successfully colonized one novel type of habitat after another: for example, marine oil spills, plastic floating in the oceans, industrial brownfields, and even the interior of the International Space Station.

However, it turns out that one extreme environment harboring a specialized community of highly adapted microbes is much closer to home: inside microwaves. This finding has now been reported for the first time by researchers from Spain in a study in Frontiers in Microbiology . It's not only important from the perspective of hygiene, but could also inspire biotechnological applications—if the strains found inside microwaves can be put to good use in industrial processes that require especially hardy bacteria.

"Our results reveal that domestic microwaves have a more 'anthropized' microbiome, similar to kitchen surfaces, while laboratory microwaves harbor bacteria that are more resistant to radiation," said Daniel Torrent, one of the authors, and a researcher at the start-up Darwin Bioprospecting Excellence SL in Paterna, Spain.

Torrent and colleagues sampled microbes from inside 30 microwaves: 10 each from single-household kitchens, another 10 from shared domestic spaces--for example, corporate centers, scientific institutes, and cafeterias--and 10 from molecular biology and microbiology laboratories. The aim behind this sampling scheme was to see if these microbial communities are influenced by food interactions and user habits.

The team used two complementary methods to inventorize the microbial diversity : next-generation sequencing and cultivation of 101 strains in five different media.

A biodiverse microbiome right at home

In total, the researchers found 747 different genera within 25 bacterial phyla. The most frequently encountered phyla were Firmicutes, Actinobacteria, and especially Proteobacteria.

They found that the composition of the typical microbial community partly overlapped between shared domestic and single-household domestic microwaves, while laboratory microwaves were quite different. The diversity was lowest in single-household microwaves, and highest in laboratory ones.

Members of genera Acinetobacter, Bhargavaea, Brevibacterium, Brevundimonas, Dermacoccus, Klebsiella, Pantoea, Pseudoxanthomonas and Rhizobium were found only in domestic microwaves, whereas Arthrobacter, Enterobacter, Janibacter, Methylobacterium, Neobacillus, Nocardioides, Novosphingobium, Paenibacillus, Peribacillus, Planococcus, Rothia, Sporosarcina, and Terribacillus were found only in shared-domestic ones.

Nonomuraea bacteria were isolated exclusively from laboratory microwaves. There, Delftia, Micrococcus, Deinocococcus and one unidentified genus of the phylum Cyanobacteria were also common, found in significantly greater frequencies than in domestic ones.

The authors also compared the observed diversity with that in specialized habitats reported in the literature. As expected, the microbiome in microwaves resembled that found on typical kitchen surfaces.

"Some species of genera found in domestic microwaves, such as Klebsiella, Enterococcus and Aeromonas, may pose a risk to human health. However, it is important to note that the microbial population found in microwaves does not present a unique or increased risk compared to other common kitchen surfaces," said Torrent.

Parallel evolution

However, it was also similar to the microbiome in an industrial habitat: namely, on solar panels. The authors proposed that the constant thermal shock, electromagnetic radiation , and desiccation in such highly irradiated environments has repeatedly selected for highly resistant microbes, in the same manner as in microwaves.

"For both the general public and laboratory personnel, we recommend regularly disinfecting microwaves with a diluted bleach solution or a commercially available disinfectant spray. In addition, it is important to wipe down the interior surfaces with a damp cloth after each use to remove any residue and to clean up spills immediately to prevent the growth of bacteria," recommended Torrent.

Journal information: Frontiers in Microbiology

Provided by Frontiers

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The Physics of Cold Water May Have Jump-Started Complex Life

The original version of this story appeared in Quanta Magazine .

Once upon a time, long ago, the world was encased in ice. That’s the tale told by sedimentary rock in the tropics, many geologists believe. Hundreds of millions of years ago, glaciers and sea ice covered the globe. The most extreme scenarios suggest a layer of ice several meters thick even at the equator.

This event has been called Snowball Earth, and you’d think it would be a terrible time to be alive—and maybe, for some organisms, it was. However, in a warmer period between glaciations, the first evidence of multicellular animals appears, according to some interpretations of the geological record. Life had taken a leap. How could the seeming desolation of a Snowball Earth line up with this burst of biological innovation?

A series of papers from the lab of Carl Simpson proposes an answer linked to a fundamental physical fact: As seawater gets colder, it gets more viscous, and therefore more difficult for very small organisms to navigate. Imagine swimming through honey rather than water. If microscopic organisms struggled to get enough food to survive under these conditions, as Simpson’s modeling work has implied, they would be placed under pressure to change—perhaps by developing ways to hang on to each other, form larger groups, and move through the water with greater force. Maybe some of these changes contributed to the beginning of multicellular animal life.

To test the idea, Simpson, a paleobiologist at the University of Colorado, Boulder, and his team conducted an experiment designed to see what a modern single-celled organism does when confronted with higher viscosity. Over the course of a month, he and his graduate student Andrea Halling watched how a type of green algae—members of a lab-friendly species that swims with a tail-like flagellum—formed larger, more coordinated groups as they encountered thicker gel. The algae collectively motored through the fluid to keep up their feeding pace. And, intriguingly, the groups of cells remained stuck together for 100 generations after the experiment ended.

The research offers a novel take on the emergence of multicellular life, said Phoebe Cohen , a paleontologist at Williams College who has spoken with Simpson about his idea over the years but was otherwise uninvolved with the work. The field is overflowing with papers about triggers for the evolution of animal multicellularity that draw on geochemical measurements, she said, but few consider the biology of individual organisms.

To re-create Snowball Earth conditions in the lab, biologists placed swimming algal cells into gel of varying viscosity. The cells that made it to the thickest, outer layer displayed signs of collective behavior—a potential step toward multicellularity.

“I’m very charmed by the idea, by the experimental setup as well,” Cohen said. “It’s really wonderful to see work saying: What’s actually going on here? How are these early organisms actually experiencing their environment?”

The experiment comes with a few caveats, and the paper has yet to be peer-reviewed; Simpson posted a preprint on biorxiv.org earlier this year. But it suggests that if Snowball Earth did act as a trigger for the evolution of complex life, it might be due to the physics of cold water.

A Frozen Paradox

“Snowball Earth” was on everyone’s lips when Simpson was an undergraduate in the late 1990s. In 1992, the geochemist Joseph Kirschvink had pointed out that there was good geological evidence for a global glaciation event in the ancient past; crucially, he provided a model for how all that ice might have been coerced to melt again. Then, in 1998, the Harvard geologist Paul Hoffman and colleagues published a landmark paper that applied these ideas to observations of sedimentary deposits in Namibia. They agreed: The rocks indicated the presence of glaciers in the warmest parts of the world around 700 million years ago.

Even back then, the timing of Snowball Earth troubled Simpson. “That was a total paradox for me,” he said. “There’s no way Snowball Earth was real, given how much interesting evolution was happening at the time.” Before Snowball Earth, fossils are tiny, he said. Afterward, they are big and complicated.

It is difficult to precisely date when animals arose, but an estimate from molecular clocks—which use mutation rates to estimate the passage of time—suggests that the last common ancestor of multicellular animals emerged during the era known as the Sturtian Snowball Earth, sometime between 717 million and 660 million years ago. Large, unmistakably multicellular animals appear in the fossil record tens of millions of years after the Earth melted following another, shorter Snowball Earth period around 635 million years ago.

The paradox—a planet seemingly hostile to life giving evolution a major push—continued to perplex Simpson throughout his schooling and into his professional life. In 2018, as an assistant professor, he had an insight: As seawater gets colder, it grows thicker. It’s basic physics—the density and viscosity of water molecules rises as the temperature drops. Under the conditions of Snowball Earth, the ocean would have been twice or even four times as viscous as it was before the planet froze over.

Simpson wondered what it would have been like to be a microscopic organism in the ocean during Snowball Earth. Maybe the whole thing wasn’t so paradoxical after all.

To very small single-celled creatures, thick seawater would have posed some big problems. Bacteria feed by diffusion—the movement of nutrients through water from areas of high concentration to low concentration—and tend to wait for food to come to them. However, at low temperatures, diffusion slows down. Nutrients don’t travel as quickly or as far. For cells, living in a cold and more viscous fluid means getting less to eat. Even very small organisms that can propel themselves, such as cells with flagella, move more slowly in cold water. As a result, they encounter food less frequently.

A bigger organism, on the other hand, can navigate thicker waters without much trouble. A cluster of cells has the benefit of inertia: Their combined mass is large enough to allow them to build up steam and barrel through thicker fluid. “At some point, you are too big for this to matter,” Simpson said.

In 2021, he published his hypothesis that Snowball Earth viscosities would have put a significant strain on organisms’ ability to feed themselves and could have spurred some to evolve multicellularity. Then, with collaborators at the Santa Fe Institute, he designed mathematical models of small creatures—single cells that fed by diffusion and self-propelling cells that fed by moving around—living in thicker and thicker fluids. In the models, posted to biorxiv.org at the end of 2023 and recently published in the peer-reviewed Proceedings of the Royal Society B , the diffusion feeders responded to thicker fluids by shrinking in size. The self-propelling cells, equipped by the equations with the ability to cling together if needed, formed larger and larger multicellular groups. This suggested that if there were already multicellular organisms when Snowball Earth occurred—or at least organisms with the ability to take on multicellular forms—the thicker fluid could have given them a reason to get bigger.

Paleobiologist Carl Simpson has led a body of work—computer modeling and experiments with living organisms—to study whether the physics of cold water causes cells to act collectively like a multicellular creature.

The results were intriguing, but they were only computer models. Simpson thought: Well, what if they did this with real organisms?

The geologist Boswell Wing, a colleague at the University of Colorado, Boulder, had a colony of Chlamydomonas reinhardtii in his lab. These algae have twirling flagella that allow them to move under their own power. They are usually unicellular. But they can switch into a multicellular form under certain stressful conditions. Would higher viscosity, like that of the oceans during Snowball Earth, prove to be one of them?

Life in Thick Water

There’s no way for biologists to travel back in time to test the real conditions of Snowball Earth, but they can try to re-create aspects of them in the lab. In an enormous, custom-made petri dish, Halling and Simpson created a bull’s-eye target of agar gel—their own experimental gauntlet of viscosity. At the center, it was the standard viscosity used for growing these algae in the lab. Moving outward, each concentric ring had higher and higher viscosity, finally reaching a medium with four times the standard level. The scientists placed the algae in the middle, turned on a camera, and left them alone for 30 days—enough time for about 70 generations of algae to live, swim around for nutrients and die.

Andrea Halling led experiments with living creatures to see how life might have responded to evolutionary pressures 600 million years ago.

Halling and Simpson suspected that as the algae reproduced and crowded the center circle of normal viscosity, any algal cells that could handle the thicker medium would spread outward. Perhaps those that reached the outermost ring would look and behave differently from those that remained in the center.

Simpson was particularly curious as to whether algae that made it into the highest viscosity ring would find ways to increase their swimming speed. The algae are photosynthetic, so they get energy from the sun. But they need to pick up nutrients such as phosphorus from the environment, so movement is still important to their survival. Maintaining the same level of nutrients in high-viscosity surroundings would require them to find a way to keep up their speed.

After 30 days, the algae in the middle were still unicellular. As the scientists put algae from thicker and thicker rings under the microscope, however, they found larger clumps of cells. The very largest were wads of hundreds. But what interested Simpson the most were mobile clusters of four to 16 cells, arranged so that their flagella were all on the outside. These clusters moved around by coordinating the movement of their flagella, the ones at the back of the cluster holding still, the ones at the front wriggling.

Comparing the speed of these clusters to the single cells in the middle revealed something interesting. “They all swim at the same speed,” Simpson said. By working together as a collective, the algae could preserve their mobility. “I was really pleased,” he said. “With the coarse mathematical framework, there were a few predictions I could make. To actually see it empirically means there’s something to this idea.”

Intriguingly, when the scientists took these little clusters from the high-viscosity gel and put them back at low viscosity, the cells stuck together. They remained this way, in fact, for as long as the scientists continued to watch them, about 100 more generations. Clearly, whatever changes they underwent to survive at high viscosity were hard to reverse, Simpson said—perhaps a move toward evolution rather than a short-term shift.

ILLUSTRATION Caption: In gel as viscous as ancient oceans, algal cells began working together. They clumped up and coordinated the movements of their tail-like flagella to swim more quickly. When placed back in normal viscosity, they remained together. Credit: Andrea Halling

Modern-day algae are not early animals. But the fact that these physical pressures forced a unicellular creature into an alternate way of life that was hard to reverse feels quite powerful, Simpson said. He suspects that if scientists explore the idea that when organisms are very small, viscosity dominates their existence, we could learn something about conditions that might have led to the explosion of large forms of life.

A Cell’s Perspective

As large creatures, we don’t think much about the thickness of the fluids around us. It’s not a part of our daily lived experience, and we are so big that viscosity doesn’t impinge on us very much. The ability to move easily—relatively speaking—is something we take for granted. From the time Simpson first realized that such limits on movement could be a monumental obstacle to microscopic life, he hasn’t been able to stop thinking about it. Viscosity may have mattered quite a lot in the origins of complex life, whenever that was.

“[This perspective] allows us to think about the deep-time history of this transition,” Simpson said, “and what was going on in Earth’s history when all the obligately complicated multicellular groups evolved, which is relatively close to each other, we think.”

Other researchers find Simpson’s ideas quite novel. Before Simpson, no one seems to have thought very much about organisms’ physical experience of being in the ocean during Snowball Earth, said Nick Butterfield of the University of Cambridge, who studies the evolution of early life. He cheerfully noted, however, that “Carl’s idea is fringe.” That’s because the vast majority of theories about Snowball Earth’s influence on the evolution of multicellular animals, plants, and algae focus on how levels of oxygen, inferred from isotope levels in rocks, could have tipped the scales in one way or another, he said.

That novelty is a strength, said the geobiologist Jochen Brocks of the Australian National University. However, in his assessment, Simpson’s hypothesis makes a few logical leaps that don’t hold up. It’s not clear that the earliest animals would have been swimming freely in water, Brocks said. Some of the first fossils that can be confidently called “animals” were anchored on the ocean floor.

Perhaps more importantly, the timeline of animal origins is very uncertain. Some estimates suggest that the Snowball Earth period might line up with the last common ancestor of animals. But these are based on molecular inferences from DNA that are hard to confirm, Brocks said. In his opinion, it’s difficult to say how much importance to assign to this era. Butterfield also remarked on this uncertainty: “There’s no evidence of anything getting large until quite a bit after [Snowball Earth].”

That said, Brocks found Simpson’s experiment quite clever and beautiful. The fact that organisms might respond to high viscosity by developing collective behavior deserves to be better understood, he said—whether Snowball Earth led to the evolution of complex animal life or not.

“Putting this into our repertoire of thinking about why these things evolved—that is the value of the entire thing,” he said. “It doesn’t matter if it was Snowball Earth. It doesn’t matter if it happened before or after. Just the idea that it can happen, and happen quickly.”

Brocks is curious about what would happen if a similar experiment were performed with choanoflagellates, little creatures that are more closely related to animals than algae are. They rely entirely on hunting to get food—they can’t photosynthesize—so they would be especially vulnerable to slowdowns caused by high viscosity. If they started to take on multicellular forms under those conditions, that would suggest that Simpson’s results represent a more general truth about how life responds to its environment. “It would be absolutely ultra-exciting,” he said.

Simpson is, in fact, currently working with choanoflagellates. Right now, he is trying to understand how they live .

“They’re really beautiful and complicated creatures,” he said. They can take on many different forms: There are fast swimmers with long flagella, slow swimmers that meander, ones that stick to a surface to grow. “They can grow these little tendrils off the tip and walk around like on stilts; they have sex, and they fuse, and they form chain colonies and rosette colonies … and if you squeeze them, apparently they’ll lose their flagella and turn into an amoeba,” he said. When it comes to responding to the challenges of a radical new environment, he reflected, “they’ve got a lot to work with.”

Original story reprinted with permission from Quanta Magazine , an editorially independent publication of the Simons Foundation whose mission is to enhance public understanding of science by covering research developments and trends in mathematics and the physical and life sciences.

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Sparks fly when you microwave grapes: here’s the science of why

• When you put two grape hemispheres close together in a microwave oven, they put on a spectacular light show.
• The microwaves create a plasma, but the complex physics of why this occurs has been a point of contention among theorists.
• At last, a high-precision experiment has pinned down why, and it’s simply classical electromagnetism at work, not a complicated resonance.

For more than 20 years, microwaving grapes has been a popular trick for creating a plasma — and a spectacular, if messy, show — right in your own home. The trick, as reported all over the internet, is to:

• take a grape
• cut it very neatly in half
• except to leave a thin bridge of “grape skin” connecting the hemispheres
• place it in the microwave (without the rotating tray)

And then sit back and watch the sparks fly!

It was assumed, by many, that the sparks were caused simply by electrical conduction: The microwaves interacted with the grapes, created a difference in the electric potential between the two hemispheres, and when the potential became great enough, current flowed. When that current flowed across the grape skin, it heated it up due to the skin’s electrical resistance, and as a result, electrons were kicked off of their atomic nuclei, creating the plasma effect that’s so prominently visible. There’s only one problem with this explanation: everything. Here’s the science of what actually causes grapes to spark in a microwave, and how we figured it out.

The first thing we’d want to do, whenever we formulate any hypothesis, is to test the premise it rests on. In other words, when we have an idea about how things work, we don’t just put that idea to the test; we go back to the starting point — our assumptions that led us to form our hypothesis in the first place — and make sure that they’re actually a valid place to start.

In this case, the assumption is that the grape needs to be split so that the two hemispheres are almost completely severed, but not quite. There needs to be a thin film, one that’s solid but lacks the electrical conductivity of the aqueous interior of a grape that connects the two hemispheres.

The simplest test we could perform to see if that’s even the case is to take two completely separate grapes and to repeat the experiment. Instead of a single grape cleaved neatly and almost perfectly in half, we’d take two distinct grapes and place them close together: so close that they’re almost, but not quite, touching. If electrical conduction were the mechanism at play, there would be no sparks, no plasma, and no exchange of electric charge.

Clearly, when we perform this experiment, we can see the flaw in our assumption that electrical conduction is the mechanism behind the sparking between two grapes. We can also see that grape skin is not an essential part of this process, that a physical connection between the two “sides” of the experiment are not necessary, and that some other mechanism must play a role in order to explain what we observe.

In 2019, a team of three scientists — Hamza Khattak, Pablo Bianucci, and Aaron Slepkov — put forth a paper that asserted resonance was to blame. The grapes themselves behave as resonant cavities, and even though the microwaves themselves have a wavelength that’s about 10 times the physical size of a grape, the electromagnetic fields generated by those microwaves become concentrated within the grapes themselves. The authors then surmised that this resonance winds up creating “hotspots” on the grapes themselves, in particular at the junction between two grapes.

By combining thermal imaging with computer simulations, they believed they had finally explained this longstanding household puzzle.

The key to their conclusions came from the thermal imaging studies. Whether using two grapes or a pair of grape-sized hydrogels, they turned a heat-measuring infrared camera onto these objects while they were being microwaved. If the microwaves were heating the internal material evenly, you’d expect the temperature to rise equally across the grapes and/or hydrogels. Only if there were some sort of uneven heating occurring — where the objects developed one or more “hotspots” on them — would you resort to a more complicated explanation.

But that latter situation, where hotspots developed, was precisely what the researchers observed. In particular, they saw that the hotspots didn’t just develop anywhere, but at the junction between the two objects. Whether they used two hemispheres connected by a thin bridge, two skin-off grapes, or two hydrogel spheres, the same phenomenon ensued: the heating occurs primarily in the location where these two objects interface with one another.

What was really exciting and unexpected, however, was what occurred where the two surfaces touched: it compressed the wavelength of the microwaves by a factor of ~80 or so, an unprecedented enhancement.

By putting thermal paper in the thin air gap between those two grapes, they were able to see what sort of “etching” was being deposited on this paper. In theory, the resolution of that etching should be limited by what we call the diffraction limit of electromagnetic waves: half the size of the full wavelength. For the microwaves found in your microwave oven, that would correspond to about 6.4 centimeters (2.5 inches) in length: significantly larger than even the grape itself.

Sure, light changes its wavelength when you pass it through a medium, and a medium like water, a hydrogel, or the interior of a grape will also possess different dielectric properties than air or a vacuum. But somehow, the etchings were only ~1.5 millimeters (0.06 inches) in size. Because of that observation, the authors concluded that the microwaves were being compressed by a factor of more than ~40 at the interface between the two objects.

If true, it would have profound implications for photonics: enabling researchers to use light to achieve resolutions that exceed the diffraction limit, something that’s long been thought impossible .

But is that correct? It’s one thing to propose a theory that successfully explains what you see in one circumstance. Although when that explanation then results in a prediction that’s thought to be impossible, you can’t simply accept it at face value. It’s absolutely vital to perform that critical test yourself and see if what’s predicted is what occurs.

Alternatively, however, you can put the underlying assumptions to the test, which is precisely what the research team of M. S. Lin and their collaborators did in October of 2021 in the Open Access journal Physics of Plasmas.

Instead of a buildup of hotspots owing to resonance, the team hypothesized an alternative mechanism: a buildup of the electric field in the small gap between the two liquid spheres, such as grapes or hydrogels. They visualize the two spheres as electric dipoles, where equal and opposite electric charges build up on the two sides of the spheres. This polarization results in a large electric potential in the gap between the spheres, and when it gets large enough, a spark simply jumps the gap: a purely electrical phenomenon. In fact, if you’ve ever turned the crank on a Wimshurst machine , exactly the same phenomenon causes the sparks there: exceeding the breakdown voltage of the air separating the two spheres.

This is interesting, because a buildup of electric charge and an exchange of electrical energy through a discharge can also cause rapid and localized heating. In other words, the explanation proposed by the earlier study, of an electromagnetic hotspot, isn’t the only game in town. Instead, an electrical hotspot could just as easily be the culprit. In this newer explanation, there’s the additional benefit that no defiance of the diffraction limit needs to be hypothesized. If the sparking is electrical in nature rather than electromagnetic — meaning that it’s based on the transfer of electrons rather than the resonant buildup of light — then the entire experiment has nothing to do with the diffraction limit at all.

The key, of course, is to figure out what critical test to perform to determine which of these two explanations best accounts for the phenomenon we’re investigating. Fortunately, there’s a very simple test we can perform. If there are electromagnetic hotspots forming on the surfaces of the two spheres, it will generate increased radiation pressure between them, causing them to repel. However, if these are electrical hotspots produced by the buildup of opposite charges on either sphere across the gap, there will be an attractive electrical force instead.

It seems pretty simple, then, right? All we have to do, if we want to rule one of these two possible explanations out, is to have those two spheres begin a very small distance apart and then apply the microwaves.

• If the electrical hotspot explanation is correct, then that means an electric field is causing both spheres to polarize. If the spheres are lined up along the direction of the electric field, there will be a large voltage generated between them, followed by the two spheres moving closer together, followed by sparks and a plasma breakdown. If the spheres are lined up perpendicular to the electric field, however, there should be no net effect.
• If the electromagnetic hotspot explanation is correct, then that means there will be changing electromagnetic fields inside and outside the water droplet, and the two droplets should develop hotspots, repel, and spark regardless of how they’re oriented within the microwave.

This is what we ideally want: a way to tell the two scenarios apart. All we need to do, if we want to invalidate (at least) one of them, is to do the experiments ourselves.

The first experiment that was performed was a simple proof-of-concept of the electrical hotspot idea. Instead of using a microwave cavity, the researchers started with a parallel plate capacitor: an electrical setup where one side is loaded with positive charges and the opposite side is loaded with an equal amount of negative charges. They lined up the two spheres inside the capacitor in two different configurations, one where the spheres were parallel to the field and one where they were perpendicular.

Just as you’d anticipate, the spheres lined up in the direction of the electric field polarized, attracted, and swiftly heated up, while the ones lined up perpendicular to the electric field neither moved nor heated up at all. The next step was the most critical: to subject the two spheres to microwave radiation and to measure, with high-speed photography and to great precision, whether their initial motion would be toward or away from one another. If it’s attractive, that supports the electrical hotspot idea, while if it’s repulsive, it would instead support the electromagnetic hotspot idea.

As the above video clearly demonstrates, these two grape-sized spheres, driven by microwave radiation and an electric potential, initially separated by just 1.5 millimeters (about 0.06 inches), become attracted to one another, and move so that they practically touch. Upon (or just prior to) contact, energy is released, which eventually leads to the formation of a plasma, ionization, and a visually stunning display.

However, as spectacular as the release of energy and the ensuing plasma display is, that’s not the scientifically interesting part; the key point here is that the two spheres attracted one another. In fact, the researchers were further able to rule out the electromagnetic hotspot explanation by changing the frequency of the microwaves over a factor of ~100 or so: if it was a resonance, as the earlier study had speculated, sparks would only appear for one particular set of wavelengths. But what was experimentally seen were sparks present over all frequency ranges.

Even though electromagnetic resonances may be present, they are not the driving factor behind the creation of sparks and plasmas. An electrical discharge from air arcing is what’s responsible. Furthermore, by testing this at both low frequencies (27 MHz) and high frequencies (2450 MHz), and seeing approximately equal attractive motions, the researchers were able to demonstrate that the electromagnetic hotspot idea, which should be maximized in the latter case, could not generate even the slightest observable repulsive force.

It’s still great fun, even if a bit unsafe, to microwave two grapes a very small distance apart, and watch the sparks fly. You are, in fact, generating a plasma in your microwave, as electrons are being ionized from the atoms and molecules present at the interface of these two spheres.

But why is that happening? What’s causing this fantastic reaction?

An earlier idea, that electromagnetic hotspots are forming within these spheres as they act like resonant cavities, has now been experimentally disfavored. Instead, it’s simply an electrical discharge occurring between two heavily charged-up surfaces due to their polarization. As is so often the case, scientific investigation uncovers different aspects of a particular problem one at a time. Through the process of responsible inquiry, we slowly assemble a better picture of the reality we all inhabit.

Your Microwave Is Teeming With Bacteria, Study Suggests

Researchers found thriving communities of microbes in microwave ovens used in home kitchens, shared spaces and laboratories

Daily Correspondent

You’ve heard of the gut microbiome —the community of bacteria, viruses and fungi that help keep humans and other animals healthy. But what about the microwave microbiome?

New research finds that microwave ovens are hosts to their own distinct communities of microbes, whether in home kitchens or office spaces. Many of these microorganisms can survive the radiation that warms food, challenging the long-held belief that microwaves successfully kill bacteria that may be harmful to human health.

Researchers described their findings in a new paper published Wednesday in the journal Frontiers in Microbiology .

Home cooks shouldn’t panic, however—their microwaves likely aren’t any dirtier than any other parts of the kitchen. However, the findings should serve as a reminder that these appliances need to be cleaned regularly, too.

“A microwave is not a pure, pristine place,” says study co-author Manuel Porcar , a microbiologist at the University of Valencia in Spain, to Nature News ’ Alix Soliman.

Past studies have found microbiomes in other household appliances, including coffee makers and dishwashers . But researchers were curious to know whether the same communities exist inside microwave ovens , which use invisible electromagnetic waves to excite water molecules inside foods. As the molecules vibrate, they produce heat.

The team swabbed the insides of 30 microwaves in homes, scientific laboratories and shared kitchens, such as in office spaces and cafeterias. Then, they cultured their samples and waited to see which, if any, microorganisms flourished. They also sequenced the DNA in their samples.

In the end, they cultivated 101 strains from the samples, representing 747 different genera of bacteria. Many were strains that are often found on human skin, and a few were known to cause food-borne illnesses.

As suspected, each microwave’s location affected its microbiome. For instance, microwaves used in laboratories had the most diverse bacteria—including “ extremophiles ,” or microbes that can withstand harsh conditions.

“We hypothesize that microwaves actually select, from the pool of bacteria present in the air and surfaces, those able to resist radiation,” Porcar tells Newsweek ’s Pandora Dewan.

The discovery of extremophiles in microwaves is not all that surprising, given that they can live in “almost any extreme-exposure environment,” says Belinda Ferrari , a microbiologist at the University of New South Wales in Australia who was not involved in the research, to New Scientist ’s James Woodford. Extremophiles have been found in hydrothermal vents , inside Earth’s crust, on Antarctica , in the stratosphere and beyond.

“They can adapt to everything,” she adds.

Those hardy microorganisms dwelling in microwaves could have other possible uses, such as cleaning up toxic waste, per Nature News .

In the future, the team hopes to explore how extremophiles evolve within microwaves over time. Another possible experiment might involve sampling microwaves both before and after cleaning, Ferrari suggests to New Scientist .

But for now, microwave users might want to brush up on their cleaning skills.

“We recommend regularly disinfecting microwaves with a diluted bleach solution or a commercially available disinfectant spray,” says study co-author Daniel Torrent, a researcher at the biotechnology startup Darwin Bioprospecting Excellence SL, in a statement . “In addition, it is important to wipe down the interior surfaces with a damp cloth after each use to remove any residue and to clean up spills immediately to prevent the growth of bacteria.”

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Sarah Kuta is a writer and editor based in Longmont, Colorado. She covers history, science, travel, food and beverage, sustainability, economics and other topics.

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Why does microwaved water kill plants? [closed]

I've read tons of articles about microwaved water klling plants and the most of them said it was a myth. So I decided to do this experiment myself on cress plants. I repeated the experiment three times, displaying them to two kinds of stress - dark or stopping watering them. In all three experiments, the microwaved samples died first.

Does anybody know what could microwave possibly do to the water, causing the plants to die?

• quantum-mechanics
• electromagnetism

• 2 $\begingroup$ Related: Does microwaved water kill plants? $\endgroup$ –  lemon Commented Feb 24, 2016 at 20:49

If you allowed the water to cool to room temperature you should be alright.

Snopes.com has done some research on this claim, and you can read their report here: http://www.snopes.com/science/microwave/plants.asp

They conducted a blind-study with boiled on a gas stove, boiled in a microwave, and the third was not boiled at all. All of the water came from the same source, and it was all allowed to cool to room temperature prior to being used to water the three sets of plants.

So you may wish to conduct your experiment in a more controlled fashion, with more plants.

Not the answer you're looking for? Browse other questions tagged quantum-mechanics electromagnetism water microwaves or ask your own question .

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The email features pictures of plants supposedly watered either with microwaved water or with water that has been heated on a stove top. Supposedly this little research gem was carried out by a student as a science fair project. And guess what? The microwave watered plants wither while the others flourish! One can come up with all sorts of possibilities explaining why differences could exist even if a legitimate attempt were made to carry out such an experiment properly. Was the soil the same in the two plants? Were they given equal amounts of water? Could they have been exposed to different lighting conditions? Was there some difference in the seeds? But before even asking such questions how about asking if pictures can lie? Absolutely! It isn’t very hard to take a series of two plants side by side and ensure that one thrives while the other dies. All you have to do is water one and not the other.

Of course the possibility that this is the way the pictures were created does not prove the case. Heating water in a microwave oven does nothing other than raise its temperature. Any talk about “the structure or energy of the water being compromised” is plain bunk. Water has no structure other than an attraction between the partially positively charged hydrogens in one molecule and the partially negatively charged oxygen atoms in adjacent ones. As far as altering the energy of the water, well, yes, that’s what heat is all about. Any time anything is heated in any fashion its energy content is increased. The idea that microwaving water somehow changes its properties for the worse is plainly absurd.

But absurdly implausible arguments don’t prove that the pictures are faked either. What proves it is the good old standard of science, reproducibility. Or lack of. And we have done that. We have watered plants with microwaved water, kettle boiled water and stove top boiled water, feeling pretty silly about it, but we did it. The results? As expected, no difference. We aren’t posting any pictures because, after all, how would you know that they are not fake. So here is the choice. You can take our word that the experiment cannot be reproduced, accept that science tells us that microwaves do nothing to water other than heat it, or take at face value some pictures in a circulating email that purport to show an effect that has eluded scientists around the world but was discovered by a student pursuing a science fair project. The choice is yours.

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Does microwaved water kill plants?

I have seen this story a couple of times in my facebook newsfeed and it strikes me as highly unlikely. The story goes:

Below is a Science fair project presented by a girl in a secondary school in Sussex. In it she took filtered water and divided it into two parts. The first part she heated to boiling in a pan on the stove, and the second part she heated to boiling in a microwave. Then after cooling she used the water to water two identical plants to see if there would be any difference in the growth between the normal boiled water and the water boiled in a microwave. She was thinking that the structure or energy of the water may be compromised by microwave. As it turned out, even she was amazed at the difference, after the experiment which was repeated by her class mates a number of times and had the same result.

So does microwaved water kill plants?

Is there any structural difference between water boiled on a stove top and water boiled in a microwave?

(Bonus points for confirming/debunking any other statements in the original article. Please cite sources of evidence.)

• This is a twist on the flawed "Wifi stunts plant growth" experiment. skeptics.stackexchange.com/questions/16479/… –  nico Commented Sep 30, 2013 at 7:04
• 6 sample size n = 1 –  wim Commented Sep 30, 2013 at 12:10
• 1 Yes! Any boiling water kills plants! –  Volker Siegel Commented Jun 11, 2014 at 14:08
• "Then after cooling " –  mulllhausen Commented Jun 11, 2014 at 22:21
• My favorite of the students inherit assumptions is that which assumes that water, effectively immutable, is not exposed to all sorts of radiation on a daily basis in nature (including ionizing radiation, of which microwaves are not) –  Shane Gadsby Commented Aug 18, 2016 at 4:28

Microwave radiation and water

"She was thinking that the structure or energy of the water may be compromised by microwave."

This was debunked by snopes.com .

There is no difference in the water heated by microwaves compared to water heated by another source (like a gas flame, or electric element).

Microwaves are non-ionizing radiation, so do not alter the substance other than exciting it to higher temperatures. ( Wikipedia:Non-ionizing radiation )

From cancerresearchuk.org :

Nonionising radiation has enough energy to move things around inside a cell but not enough to change cells chemically. The radiation from a microwave oven is nonionising.

From Australian Radiation Protection and Nuclear Safety Agency :

Nonionising radiation is found at the long wavelength end of the spectrum and may have enough energy to excite molecules and atoms causing then to vibrate faster. This is very obvious in a microwave oven where the radiation causes water molecules to vibrate faster creating heat.

Skeptical analysis of the experiment

This was not a useful experiment. Using a sample size of 1 for each population is akin to the fallacy of using anecdotal evidence. This is just one instance in which one plant died and another lived. The dead plant could have had poor genes, an infestation, poor soil quality, among other things. The container they were using for the microwave water could have been contaminated with something, or used for other purposes in between waterings.

The description of the experimental method, especially the measures they took to avoid causing a difference between the two populations is extremely lacking.

The experiment which was repeated by her classmates a number of times and had the same result.

How many times? Two? Three? 300? Without more detail, this is just hearsay. And again, the story fails to describe the measures taken to prevent other causes of differences between the two populations.

• 1 The claim is that this was water. But yes, that is yet another factor that was not well-controlled in this experiment. –  user5582 Commented Sep 30, 2013 at 6:51
• 3 Heating the water in a pan on the stove could add just the trace elements missing in the soil... –  DJohnM Commented Oct 1, 2013 at 0:13
• 2 @User58220 Yes, that is a possibility. Their contamination controls were not explained. –  user5582 Commented Oct 1, 2013 at 1:27
• 2 The more amazing the result, the less likely the study was blinded. –  Wayne Conrad Commented Oct 10, 2013 at 17:01
• 4 I guess if any public-spirited parent had baby twins they could try this with milk ;) –  Benjol Commented Nov 22, 2013 at 9:28

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Microwaved water: Does it kill plants? (2)

The plants given microwaved water, in the center, are alive and well after three weeks.

A quick update on my experiment to see how feeding plants water boiled in a microwave oven affects their growth: after around three weeks, the microwave plants are doing just fine – as are the other two sets given non-microwaved water. Apologies for picture quality but hopefully it’s clear we have three sets of healthy sprouts here.

It may appear the microwave plants (komatsuna spinach mustard) are a little smaller than the others. However, the sets given straight filtered water (left) and filtered water boiled conventionally on a stove (right) have a fairly wide range of plant sizes, while the microwave ones are more uniform. On average, growth is about the same for all three pots.

At this stage, it appears that feeding plants filtered water boiled in a microwave oven (and then cooled to room temperature) has no affect on growth. If you are wondering why I am testing this, please read part 1 of the experiment . You will find more details on the original claim that microwaving water damages its structure and causes the formation of dangerous radiolytic compounds – something that would affect any food cooked in a microwave oven.

Other details and resources Part one of Microwaved water: Does it kill plants? Microwaved water plant experiment on snopes.com More images and information available on Facebook (must be logged in)

2 Responses to “Microwaved water: Does it kill plants? (2)”

Read below or add a comment...

I did a replication study with a larger sample (300 seeds per water sample), controls, blinding, etc. I can send you a copy of the ‘paper’ if you like (mail me at outeast1ATgmailDOTcom. Results were negative, though – as with your own replication here. The plants did just fine on microwaved water (unsurprisingly).

Thanks for the feedback, Pan Outeast. I’d definitely be interested in seeing the paper. In the meantime, do you have a Website or anything online? My nutritional medicine degree has taken over my life at the moment.

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Microwaves & Water

High-frequency pulsed microwave radiation interferes with the natural, electromagnetic, integrated network of water. Through this network, water is capable of absorbing, storing and transferring information. The electromagnetic hydrogen bonds, and thus the structure of water, are destabilised and water’s microbiology becomes unbalanced when microwaved.

Microwaves disturb the vital functions of water.

Hence, through today’s mobile communications technology used worldwide the entire water balance of the Earth and of all living organisms is compromised. This has drastic consequences, for without water there is no life. The human body consists of more than 70% water, in newborns the percentage of water is almost 90%. Water not only satisfies our thirst. In the human body it plays an important role in the information transfer in cells, it maintains metabolic processes, it is a binding agent for cell structures and is needed for the evacuation of waste products and poisons. All these natural abilities of water are disturbed by microwave technology – with corresponding consequences for the health of man and Nature.

In this fifth presentation from our series "How artificial electromagnetic radiation harms life", the focus is our body – Electrosmog - pure stress four our body!

In this fourth presentation from our series "How artificial electromagnetic radiation harms life", the focus is Water – The Elixir of Life: Threatened by Radiation?

In this second presentation from our series "How artificial electromagnetic radiation harms life", the focus is on the fact that all life is electrical.

How does our body deal with mobile phone radiation? Is it possible to easily recognise the effect of technical radiation on natural systems? Does radiation change water, the element on which all life is based? How do animals and plants react?Denise Ulrich pursued this question with experiments in her own laboratory. Her findings provide clear answers and show that the solution is simple.

Interview by Dr. Zac Cox, The World Foundation for Natural Science for England, of Mr. Barrie Trower, a globally recognized expert in the impact of wireless technologies on life.

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• Published: 07 August 2024

No observable non-thermal effect of microwave radiation on the growth of microtubules

• Greger Hammarin 1   na1 ,
• Per Norder 1   na1 ,
• Rajiv Harimoorthy 1 ,
• Guo Chen 1 , 2 ,
• Peter Berntsen 1 , 3 ,
• Per O. Widlund 4 ,
• Christer Stoij 5   na2 ,
• Helena Rodilla 6 ,
• Jan Swenson 2 ,
• Gisela Brändén 1 &
• Richard Neutze 1  

Scientific Reports volume  14 , Article number:  18286 ( 2024 ) Cite this article

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• Cytoskeletal proteins
• Perturbations

Despite widespread public interest in the health impact of exposure to microwave radiation, studies of the influence of microwave radiation on biological samples are often inconclusive or contradictory. Here we examine the influence of microwave radiation of frequencies 3.5 GHz, 20 GHz and 29 GHz on the growth of microtubules, which are biological nanotubes that perform diverse functions in eukaryotic cells. Since microtubules are highly polar and can extend several micrometres in length, they are predicted to be sensitive to non-ionizing radiation. Moreover, it has been speculated that tubulin dimers within microtubules might rapidly toggle between different conformations, potentially participating in computational or other cooperative processes. Our data show that exposure to microwave radiation yields a microtubule growth curve that is distorted relative to control studies utilizing a homogeneous temperature jump. However, this apparent effect of non-ionizing radiation is reproduced by control experiments using an infrared laser or hot air to heat the sample and thereby mimic the thermal history of samples exposed to microwaves. As such, no non-thermal effects of microwave radiation on microtubule growth can be assigned. Our results highlight the need for appropriate control experiments in biophysical studies that may impact on the sphere of public interest.

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Introduction.

Microwaves span the electromagnetic spectrum from wavelengths of one millimetre to one meter (300 GHz to 300 MHz). Modern technology exploits this spectral domain with applications including mobile telephones, wireless LAN, Bluetooth, navigation radar, automobile radar, communications satellites, global positioning system (GPS), military radar targeting, microwave ovens, radio astronomy and medical applications. Whether or not there may be negative health effects arising from being constantly immersed in radiation within this frequency domain has been the subject of considerable debate and controversy 1 , 2 . Public interest is particularly high concerning the widespread use of mobile telephones and telephone transmitters 3 , 4 . One well known effect of microwaves is that they induce heating. For example, the guidelines for microwave devices are focused on the thermal response and baselined at levels far below what is known to be harmful 5 . Conversely, because thermal effects are strong, any non-thermal effects of microwave (non-ionizing) radiation may be overlooked.

Theoretical suggestions for protein resonances in this frequency domain 6 , 7 , 8 have long been proposed but lack conclusive supporting experimental evidence. The existence of such resonances has also been challenged on the basis that vibrational damping will suppress such processes 9 . Protein normal modes may be selectively enhanced in lysozyme crystals exposed to radiation in the THz domain 10 , but an earlier study of the influence of microwave radiation on lysozyme crystals did not reveal non-thermal structural effects 11 and small angle X-ray scattering studies of the effect of THz radiation on proteins did not reveal structural changes 12 . Other claims of non-thermal effects of microwave radiation observed on cells or macromolecules often rely heavily on knowledge of microwave physics for their interpretation 7 , 13 , 14 , 15 and consequently struggle to convince across interdisciplinary barriers. Other studies on living cells do not show any non-thermal effects 16 , and one high-profile article that claimed a non-thermal heat-shock response to microwave radiation 17 was later retracted because the experimental conditions actually involved a modest temperature rise 18 . For these reasons, the studies of non-thermal effects of microwaves on cells have not been reproducible and explanations have been offered to describe this problem 19 .

Here we examine the influence of an applied microwave field on the growth of microtubules by monitoring time-dependent changes in the sample’s turbidity 20 . Tubulin is a protein that is integral to the eukaryotic cytoskeleton and exists in solution as a dimer of two globular proteins, α and β tubulin. These dimers assemble into dynamical polymeric tubes in the presence of Guanosine triphosphate (GTP, a major cellular metabolite) that are approximately 24 nm in diameter and can extend up to several micrometres in length. Microtubules are critical for cellular organization, motility, transport and mitosis 21 . Microtubules are also dynamically instable due to a constant process of assembly and disassembly, which leads to periods of rapid growth interrupted by periods of rapid shortening. The growth of microtubules from tubulin dimers can be described as comprising three phases: nucleation, elongation and saturation 22 . During nucleation, new microtubule aggregates are generated from tubulin dimers. As these nuclei grow, they pass through their so-called least-stable complex, after which they enter the elongation phase by the addition of dimers onto these previously formed nuclei. At saturation the rate of growth slows as the number of free tubulin dimers become relatively scarce. An important mechanistic idea underpinning this process is that microtubules are believed to assemble in vitro via the formation of small sheets which grow wider and longer and eventually fold into tubes once they achieve their full complement of approximately thirteen proto-filaments (thirteen tubulin dimers per turn) in width 22 . Since microtubules are highly polar, and in some respects can be imagined as having characteristics similar to radio antennae but on a micrometre scale, they have been suggested to be sensitive to non-thermal effects of microwave radiation 23 , 24 .

To investigate non-thermal influences of microwave radiation on the growth of microtubules, we measured the polymerization of tubulin in response to electromagnetic radiation 3.5 GHz, 20 GHz and 29 GHz in frequency. These electromagnetic fields were applied using a waveguide with a plate separation of 1 mm, and the peak-to-peak voltages ranged from -2 V to 2 V (specific details and Specific Absorption Rate (SAR) values given in Table 1 ). These three frequencies also span the domain used by 5G networks (0.6–29 GHz). Changes in sample optical density were followed as a time-dependent increase in turbidity used as a proxy for microtubule formation 25 . An infrared camera characterized the spatial distribution of sample heating, with the sample’s optical density (O.D.) being measured at the point where heating from the microwave field was strongest. Simultaneous measurements of the sample’s optical density and temperature allowed both thermal and non-thermal responses to be characterized. We observe that the growth curves for microtubules in samples exposed to 20 GHz and 29 GHz, radiation depart from the growth trajectories observed at the same temperature when there is no exposure to microwaves, whereas samples exposed to 3.5 GHz radiation do not show this discrepancy. These apparent non-thermal effects, however, could be reconciled with additional control studies in which the thermal history of the sample as it entered the microwave field was mimicked. These findings illustrate how false conclusions may arise if subtleties within the experimental design are not appreciated and emphasises the need for careful design of control experiments given the widespread concerns regarding the effect of microwaves on public health.

Exposure of samples to microwave fields

We aimed to characterise the response of microtubules to an applied oscillating electromagnetic field. Having a background in X-ray scattering 26 , 27 , we designed a device which would support both light-scattering and X-ray scattering measurements. To this end a parallel-plate waveguide-based flow-cell was purpose built to deliver AC fields onto a quartz capillary containing the sample (Fig.  1 ). Both waveguide plates were 64 mm long, 5 mm wide and were separated by just over 1 mm. The waveguide was shaped so that only the central part of the waveguide, 25 mm long, ran adjacent to the capillary. A coaxial cable fed the GHz fields from a signal generator through the waveguide, which was terminated on a 50 Ω resistor. The waveguide was designed to work optimally within the frequency domain correlating with peak dielectric losses in water, which at room temperature is close to 20 GHz 28 .

Experimental apparatus used to measure changes in optical density (O.D.) of microtubule samples during exposure to 3.5–29 GHz AC fields. ( a ) Photograph of the waveguide used to deliver 3.5 to 29 GHz radiation onto a 1 mm diameter quartz capillary in which the sample was held. The white box indicates the region shown in the next panel. The white bar represents 2 cm. ( b ) Infrared image of the sample within a quartz capillary completely filled with water during exposure to 20 GHz radiation. For this image the IR camera was mounted directly in front of the flow cell. The measurement spot during measurements is marked with a black circle. Colour bar inset shows temperature profile increase from room temperature. ( c ) Photograph of the experimental setup used to record the O.D. at 365 nm with time during simultaneous exposure to microwaves. This entire setup was enclosed within a temperature-controlled box. An infrared camera (FLIR thermographic) was used to monitor the temperature of the sample at the position at which its O.D. was recorded. ( d ) Schematic of the thermally insulated experimental setup which shows microspectrophotometer optics and connections to diode and spectrophotometer, positioning of the IR camera, hot air inlet, thermometers to measure ambient temperature, tubing connecting sample reservoir with the suction pump and electromagnetic signal generator. ( e ) Simulation of electric field inside the capillary for a 1 W input with a frequency of 20 GHz. The sample capillary is shaded light blue. The point of optical density measurement and connector ports are marked. The electric field varies along the sample in the capillary and the point at which the optical density was measured was located where the field strength was strongest. Field strength scales linearly with applied voltage.

An unavoidable consequence of sampling the effects of electromagnetic fields applied in the microwave domain is that samples are heated. Conversely, the observation of sample heating provides confidence that the device efficiently delivers microwaves onto the sample. To quantify this effect, we used a FLIR thermographic infrared camera to map the extent of water heating within the quartz capillary (Fig.  1 b , Supplementary Figure S1 ). This allowed us to establish that the energy transfer from the AC field generator to the sample was maximal near 20 GHz, where both the microwave generator and the coupling were efficient. Moreover, by imaging the microwave heating profile using the thermographic infrared camera, we could record the sample’s optical density at the point where the heating was maximal. Changes in light-scattering in the microwave exposed quartz capillary were then measured using a microspectrophotometer that was similar to an earlier design 29 (Fig.  1 c, d). The majority of experiments presented here used 20 GHz radiation, but data were also recorded at 3.5 GHz and 29 GHz. Full wave electromagnetic simulations of the device for these three different frequencies show a standing wave pattern in the electromagnetic field distribution in the sample (Fig.  1 e, Supplementary Fig.  S2 a, b). Weak oscillatory features are also visible to some extent by thermal imaging for the two higher frequency sets, although the pattern is more diffuse due to thermal diffusion (Supplementary Fig.  S1 a, d–e). Simulated S21 and S11 parameters show a similar frequency dependence as the measured values (Supplementary Fig.  S2 c, d), although the simulations slightly underestimate the losses.

20 GHz measurements were conducted with three different power output levels from the signal generator, 15 dBm (32 mW), 19 dBm (80 mW) and 23 dBm (200 mW). A fraction of the signal is lost in the coaxial cable from the signal generator to the waveguide, and this was measured as 0.8 dBm. As such, the input into the waveguide is lowered from the above values to become 26 mW, 66 mW and 166 mW respectively. By assuming that losses between the connector of the cable and the transmission line into the waveguide are negligible, assuming that the electric field strength varies linearly along the length of the waveguide, and by measuring the transmitted (S21) and reflected (S11) scattering parameters of the waveguide (Supplementary Fig.  S2 c, d) with both an empty capillary and when the capillary is filled with sample buffer, we could estimate the electromagnetic field at the sample position. The power estimated at the point at which the optical density was measured and its peak voltage are listed in Table 1 as a function of the measured input power. For an input frequency of 20 GHz and 166 mW input power, the electromagnetic field at the point of measurement is approximately 1.8 kV/m, which compares with the nominal input voltage of 4.1 kV/m.

The SAR within the sample can be calculated using the formula SAR = σ ∙E 2 /ρ. The buffer conductivity (σ) is measured to be 0.8 S/m and the sample density (ρ) is assumed to be that of water. It has been reported that polymerized microtubules can increase the conductivity of a solution by several percent, but we do not include this in our SAR estimate 30 . The calculated SAR values range between 300 and 2900 W/kg (Table 1 ). Depending upon which guidelines one compares to, which are different for different parts of the body and different frequencies, these calculated values vary from one to several orders of magnitude above the guidelines for human exposure 5 . For example, the whole-body average over time is given as a maximal exposure of 0.08 W/kg but local occupational exposures for brief intervals may allow exposures of up to 100 W/kg 5 .

Data collection and analysis

GTP is required for tubulin dimers to polymerize, but they will not polymerize until the temperature is raised above a critical temperature 31 , which is approximately 18–19 °C at the sample concentrations used for this study. This effect is used in functional assays since tubulin samples can be mixed with GTP while on ice, which arrests their nucleation and growth. As aliquots of these samples are pumped through the flow-cell to the measurement position, they are warmed by the ambient temperature of the surrounding environment and this temperature jump initiated the polymerization reaction. After reaching the point of measurement, each sample aliquot (5 μl) was held stationary during the experiment, and was then replaced with a fresh 5 µl sample for a fresh measurement. Solubilized samples of tubulin dimers are almost completely transparent to 365 nm light, whereas samples of microtubules are opaque. This allows tubulin polymerization to be followed as the relative turbidity of the sample increases with time 25 , 31 . We followed this dynamical process by recording the sample’s optical density (O.D.) with time through a 1 mm capillary using a microspectrophotometer 29 (Fig.  1 c, d).

In our waveguide, the application of 20 GHz microwave radiation onto the sampled position with an input power of 66 mW and 166 mW resulted in the sample being heated by approximately 4 °C and 7 °C respectively. It was therefore necessary to enclose the apparatus within a box (Fig.  1 d) and to set the ambient air temperature within this box lower than the target sample temperature at the position of observation by a compensatory amount (ie., 4 °C lower for 66 mW and 7 °C lower for 166 mW input power). The 29 GHz input heated samples to a very similar extent to 20 GHz input, whereas neither the 20 GHz with input power of 26 mW nor the 3.5 GHz microwave radiation visibly heated the sample (Supplementary Figure S1 a). Throughout all light-scattering measurements, the temperature at the sample position was measured using the thermographic infrared camera and the temperature values reported for all data points correspond to the temperature at the sampled position, and consequently include heating from both the surrounding environment and the microwave radiation (Table 2 , T f —T i ). Because the growth of microtubules is a stochastic process, with their nucleation being relatively slow before a more rapid elongation phase, there may be considerable run-to-run variability in the growth curves 22 , 32 . We therefore repeated each data-point on average 22 times (Table 2 , \(N\) ), although there was variation in the sample of specific runs due to outlier rejection. Data were initially rejected when we had incomplete O.D. trajectories due to bubbles in the light path. Subsequent outlier rejections were done with the MAD method, a method similar to Z-score but based on medians rather than means 33 .

Representative measurements of the time dependence of the change in the sample’s \(O.D.\) are shown in Fig.  2 a, where data were measured using 10% (by volume) glycerol, 10 mg/ml tubulin (91 μM), and 2 mM GTP, with the temperature at the sample position 34.9 ± 0.3 °C and 39.1 ± 0.4 °C. These data have been normalized to have an initial optical density ( \(O.D.\) ) of zero and a final \(O.D.\) of unity. Error bars in these curves are given as the standard error of the mean ( ie. \(\sigma /\sqrt{N-1})\) , where \(\sigma\) is the standard deviation and \(N\) is the number of repeats of each of the measurements. These data follow the approximate sigmoidal curves typically associated with microtubule nucleation, growth and saturation 22 , 25 , 31 .

Measured changes in O.D. from samples of tubulin during the growth of microtubules. ( a ) Turbidity measurements ( \(O.D\) .) with time ( \(t\) ) for samples exposed to a constant ambient temperature of 34.9 °C (blue line) and 39.1 °C (red line). Error bars represent the standard error, \(\sigma /\sqrt{N-1}\) , where \(\sigma\) is the standard deviation of a set of \(N\) measurements. These data have been normalized to have their end-point \(O.D. =1\) . ( b ) Plot of \(O.D.\) versus time on a log–log scale. These curves were approximately linear between O.D. = 0.1 and O.D. = 0.4 and the slope of this line (black dots) yielded the \(b\) -value (Eq.  2 ). Since both lines are approximately parallel, a Mann–Whitney U-test comparing \(b\) -values from each set of runs showed no significant difference (Table 3 ). ( c ) Plot of the two curves shown in A after stretching in time such that the slower curve (blue line) superimposes on the faster curve (red line) with matching \({t}_{50}\) values. ( d ) Plot of the temperature measured at the sample position using the thermographic camera. In the case of homogeneous (ambient) heating, the temperature difference between the two measurements is almost constant throughout these experiments.

In the initial phase it is possible to approximate microtubule growth using a power law 25

where \(A\) is a constant, \(b\) is the power law exponent, and \({t}_{u}\) is a unit of time introduced in order to keep the equation dimensionless. Taking the natural logarithm of both sides gives:

and a plot of \(ln(O.D)\) vs ln(t)  should yield a straight line with slope \(b\) . Moreover, the point at which the \(O.D.\) reaches 10% of its maximum value, \({t}_{10}\) , may be read from the experimental curve directly. The same data presented in Fig.  2 a are redrawn in Fig.  2 b using logarithmic axes and yield approximately straight lines over the domains \(0.1 \le O.D. \le 0.4\) , where this linear fit is represented using dotted lines.

Comparison of microtubule growth curves at different temperatures

The overriding goal of this work is to establish if measurements of the growth of microtubules show statistically significant differences in their behaviour when exposed to microwave radiation. In drawing statistical comparisons between experimentally measured curves, we examine three parameters: the final \(O.D.\) , the \({t}_{10}\) values, and the \(b\) values extracted from fitting Eq.  2 to the experimental data. From these parameters extracted from \(N\) repeats for each condition (Table 2 ), the results from two experimental conditions were compared using the Mann–Whitney U-test (also called the Wilcoxon rank sum test), which evaluates the hypothesis that two sets of measurements have different medians. The Mann–Whitney U-test is a non-parametric test and therefore does not require that data are normally distributed. This statistic test was chosen since we could not conclude that all parameters for all experimental conditions were normally distributed (Supplementary Figure S3 illustrates the results of normality checks using Anderson–Darling, One-sample Kolmogorov–Smirnov, Lilliefors and Jarque–Bera tests by labelling dataset histograms red if they fail at least one of these tests). Because microtubule nucleation and growth are stochastic processes, because we used a small volume of sample (~ 5 μl) in our flow-cell in order to optimize the microwave field-strength, and because the kinetics of microtubule growth are sensitive to multiple parameters 25 which may fluctuate slightly from run to run, there was considerable variation in these parameters from one measurement to the next. We therefore take a \(p\) -value < \({10}^{-3}\) as indicating a statistically significant difference, and this condition is usually regarded as stringent. As is illustrated in Table 3 , a weaker requirement of \(p\) -values < \(0.05\) would not change any of our major conclusions in any substantial way.

To illustrate this procedure, consider the comparison between the behaviour of microtubule growth curves at the two temperatures illustrated in Fig.  2 . As seen in Table 2 , the final \(O.D.\) and \({t}_{10}\) values vary as the temperature is varied, yet the measured \(b\) -values were relatively consistent within the experimental uncertainty of the mean values of these parameters. These observations are reflected in conclusions drawn from the Mann–Whitney U-test (Table 3 ), which show that the experimental traces from the separate measurements yield \(p\le {10}^{-3}\) for the \(O.D.\) and the \({t}_{10}\) values when comparing these measurements between any two of the three temperatures: 31.9 ± 0.6 °C, 34.9 ± 0.3 °C and 39.1 ± 0.4 °C. For example, the mean final \(O.D.\) at 39.1 °C is 49% higher than that resulting at 31.9 °C, and 16% higher than for measurements performed at 34.9 °C. This statistically significant increase in \(O.D.\) with temperature is consistent with earlier observations 25 . Similarly, since all reactions are accelerated as the temperature increases, the \({t}_{10}\) values will be considerably lower at elevated temperature, since the kinetics of the reaction are faster 25 . This is measured experimentally with \({t}_{10}\) = 57.3 ± 4.0 s at 31.9 °C, \({t}_{10}\) = 25.8 ± 1.8 s at 34.9 °C and \({t}_{10}\) = 10.3 ± 0.5 s at 39.1 °C (Table 2 ). Despite these differences, comparison of the \(b\) -values extracted using Eq.  2 for data recorded at 34.9 °C and 39.1 °C yielded a \(p\) -value of 0.10, which is not considered significantly different. This is illustrated in Fig.  2 b since the apparent slopes of the two linear-fits to the experimental data on log( \(O.D.\) ) vs. log( \(t\) ) plots are almost parallel. Indeed, Fig.  3 of reference 25 shows that log( \(O.D.\) ) vs. log( \(t\) ) plots yield parallel lines under a great variety of experimental conditions. The statistical test yielded a \(p\) -value of 0.02 when comparing b-values at 31.9 °C and 34.9 °C, which fails out threshold of \(p\le {10}^{-3}\) , but potentially indicate that the ratios of the various forwards and backwards rate-constants describing tubulin polymerization 31 , 34 may diverge slightly at the lower temperature.

Measured changes in O.D. from samples of tubulin exposed to microwaves during the growth of microtubules. ( a ) Turbidity (normalized \(O.D.\) ) with time ( \(t\) ) for samples exposed to a constant ambient temperature of 34.9 °C (blue line) and when exposed to 20 GHz microwave radiation (red line). ( b ) Plot of \(O.D.\) versus time on a log–log scale. Since these lines are not parallel, a Mann–Whitney U-test showed a significant difference when comparing \(b\) -values from the two sets of data (Table 2 ). ( c ) Plot of the two curves shown in A after stretching in time such that the faster curve (red line) superimposes on the slower curve (blue line) with matching \({t}_{50}\) values. ( d ) Plot of the temperature measured at the sample position using the thermographic camera. A larger change in temperature with time was associated with the microwave measurements.

Although microtubule polymerization is a multi-step process, including a nucleation phase, an elongation phase and a saturation phase, if the kinetics of all participating forward and backward reactions co-vary with temperature, then the shape of the resulting sigmoidal curve will be independent of temperature. One test for this hypothesis is to scale the time-variable for one set of measurements, such that the value when the average of two separate measurements reaches their mid-point \(O.D.\) (called \({t}_{50}\) ) is numerically the same for both measurements (Fig.  2 c). We can then perform a Mann–Whitney U-test on the resulting distribution of \({t}_{10}\) variables after time has been “stretched” in order to make this comparison. This procedure changes neither the \(b\) -value nor the \(O.D.\) . The statistical test results after this manipulation are given in Table 3 under the column heading “Stretched”. For example, when time-scaling was imposed and data recorded at 31.9 ± 0.6 °C, 34.9 ± 0.3 °C and 39.1 ± 0.4 °C were compared, the \(p\) -values for \({t}_{10}\) increased from < 10 –6 to 0.16, 0.23 and 0.35, none of which indicate a statistically significant difference. Thus this “time-stretching” procedure demonstrates that the ratio of \({t}_{50}\) to \({t}_{10}\) is statistically independent of the temperature at which these measurements were performed.

Comparison of microtubule growth curves when exposed to microwaves

With these tools of analysis illustrated above, we are in a position to compare the growth curves of microtubules when exposed to microwave radiation with control studies of samples held at constant temperature. Figure  3 illustrates how the presence of microwave fields change the growth-curves when using 20 GHz radiation applied at 166 mW (1.8 kV/m, SAR 2.7 kW/kg). Although the growth curve is qualitatively similar (Fig.  3 a), a log( \(O.D.\) ) vs log( \(t\) ) plot reveals that the slopes of these graphs are not parallel (Fig.  3 b). This is quantified in Table 2 , in which the average \(b\) -value at 34.9 °C of 2.21 ± 0.05 increases to 2.98 ± 0.04 as the microwave field is applied. Moreover, the Mann–Whitney U-test of the \(b\) -values for these runs give \(p\) < 10 –8 , which is a statistically significant difference. This difference is visualized more easily by applying time-stretching in order to match \({t}_{50}\) for the two measurements (Fig.  3 c), which yields a growth curve when 20 GHz radiation is applied that does not superimpose well with the 34.9 °C control which is not exposed to microwave radiation. In this case, however, the Mann–Whitney U-test after stretching yields \(p\) = 0.05 for the comparisons on \({t}_{10}\) , which we do not consider to be sufficiently low to claim a statistically significantly difference given the uncertainties in the mean after stretching.

Very similar results are recovered for measurements at 29 GHz using 166 mW of power (1.9 kV/m, SAR 2.9 kW/kg), for which again the average \(b\) -value increased to 3.06 ± 0.05 when a microwave field was applied. As previously, the statistical test yields \(p\) < 10 –8 when comparing \(b\) -values, but \(p\) = 0.03 for \({t}_{10}\) after time-stretching. As such, for both 20 GHz and 29 GHz radiation using a power of 166 mW there is a statistically significant change in the measured \(b\) -values. Moreover, for the lower applied powers of 26 mW (1 kV/m, SAR 0.8 kW/m) and 66 mW (1.3 kV/m, SAR 1.4 kW/kg) there is a shift in the mean b-values from 2.21 ± 0.04 for the constant temperature measurements at 34.9 °C, to 2.15 ± 0.05 when 26 mW of 20 GHz radiation is applied, and to 2.42 ± 0.04 when exposed to 66 mW of 20 GHz radiation. In this case the shift in \(b\) -values is significant for the 66 mW field according to the criteria used here ( \(p\) = 0.0006 according to the statistical test, Table 3 ) and there is a consistent trend to lower \(p\) -values with increasing input power. The exposure of electromagnetic fields with a frequency of 3.5 GHz (600 V/m, SAR 0.3 kW /kg) doesn not alter the b-value in a statistically significant way. We therefore conclude that the application of microwave radiation of 20 GHz or 29 GHz in frequency with an input power of 166 mW onto a volume of approximately 5 μl leads to a measurable change in the power-law describing the growth of microtubules. This is striking since the measurement of the growth of microtubules repeatedly showed that the power-law was conserved over a large variety of experimental conditions 31 .

Comparison of microtubule growth curves exposed to microwaves, infrared laser and airflow heating

In the previous section, we recovered statistically significant observable differences between the measured growth curves for microtubules raised to constant temperature relative to those exposed to microwaves. These observations raise the question whether or not this effect is the result of a previously unobserved non-thermal effect of microwave radiation that perturbs the kinetics of nucleation or growth, or if there may be more subtle thermal effects that warrant further investigation. As noted above, one consideration is that, because of the heating effect of the microwaves, the temperature of ambient environment surrounding the sample must be set a few degrees lower than in the control studies. This means that the thermal history of the sample is slightly different between the experiment using microwaves and the control, and this can be seen by comparing their temperature traces (Figs. 2 d, 3 d). Specifically, the sample’s \(O.D.\) is measured from the moment the sample reaches the position where the light from the microspectrophotometer is incident upon the capillary. Since the flow-rate from the sample on ice to the measurement position is the same for all measurements, there is a period of approximately seven seconds (transfer line of 73 μl of 1 mm inner diameter pumped at 10 μl/s) during which the sample which was held at 0 °C increases to the ambient temperature. Because the ambient temperature is lower for the microwave exposed studies, the sample is slightly cooler when it arrives at the position of measurement when exposed to microwave radiation than for the control studies, and this is apparent from the measured temperature traces at the sample position (Fig.  3 d).

To account for this discrepancy in the thermal history of the sample, we designed a control study in which the sample was raised to the end point temperature step-wise: first by holding the flow-cell in an environment in which the ambient temperature was above zero but lower than the target measurement temperature, and then using either a focused air-flow to heat the sample at the measurement position (Fig.  4 ), or by using an infrared laser to heat the sample in a focused spot and thereby raise the sample’s temperature to the target value (Fig.  5 ). As seen in Figs. 4 d and 5 d, this strategy meant that the temperature of the sample for these additional control measurements increased quite significantly during the initial phase of the light-scattering measurements, which was also the situation for the measurements on samples exposed to microwaves (Fig.  3 d). After some adjustments to better approximate the heating effect of exposure to 20 GHz microwave radiation, we observe that in these cases the \(b\) -values were also enhanced. Specifically, when an air stream was used to heat the sample above the ambient temperature in a small region surrounding the sampled position, the \(b\) -value was 2.91 ± 0.11 (Table 2 ) and yielded \(p\) < 10 –4 for a statistical comparison (Table 3 ) with the constant ambient temperature control of 34.9 °C. Conversely, \(p\) -values of 0.89 and 0.20 were recovered when the \(b\) -values were compared with measurements using 20 GHz and 29 GHz radiation with an input power of 166 mW. Similarly, the studies using an IR laser to generate a tight-temperature gradient at the sample position that mimicked the effect of heating by microwave radiation, yielded a \(b\) -value was 2.86 ± 0.04 (Table 2 ) and again \(p\) < 10 –8 in the statistical comparison (Table 3 ) with the constant ambient temperature control of 34.9 °C. In these cases, \(p\) -values of 0.09 and 0.003 were recovered when the \(b\) -values were compared with measurements using 20 GHz and 29 GHz radiation with an input power of 166 mW. The comparison against 29 GHz would have been interpreted as significant with a cut-off of \(p\) = 0.05, and we suggest this arises from the fact that that the thermal gradient of the IR laser was the steepest in comparison with the 29 GHz thermal gradient (Supplementary Figure S1 a). We therefore conclude that enhanced \(b\) -values, which in the previous section appeared to be a unique characteristic for samples exposed to microwave radiation above 20 GHz in frequency and a power of 166 mW in intensity, can also be recovered from two other experimental configurations in which the sample is heated step-wise. Thus, whereas exposure to microwave radiation in our flow-cell perturbs the kinetics of microtubule growth relative to one-step heating controls in a reproducible manner, this effect cannot be distinguished from the effect of two-step heating controls. Or conversely, although our experimental data cannot conclusively rule-out the possibility of non-thermal effects of microwave radiation on microtubules effecting their growth kinetics, the application of Occam’s razor prescribes that it is not necessary to appeal to anything other than microwave induced heating to explain the experimental data reported here.

Measured changes in \(O.D.\) for samples of tubulin exposed to microwaves compared to samples heated by a laminar of warm air during the growth of microtubules. ( a ) Turbidity (normalized \(O.D.\) ) with time ( \(t\) ) for samples exposed to 20 GHz microwave radiation (red line) and when exposed a local thermal gradient (blue line). ( b ) Plot of  \(O.D.\)  versus time on a log–log scale. Since both lines are approximately parallel, a Mann–Whitney U-test comparing  \(b\) -values from the separate runs showed no significant difference (Table 2 ). ( c ) Plot of the two curves shown in A after stretching in time such that the air heated curve (blue line) superimposes on the microwaved exposed curve (red line) with matching  \({t}_{50}\)  values. ( d ) Plot of the temperature measured at the sample position using the thermographic camera. A comparable change in temperature with time was associated with the two exposure protocols.

Measured changes in O.D. from samples of tubulin exposed to microwaves compared to samples heated by an IR laser during the growth of microtubules. ( a ) Turbidity (normalized  \(O.D.\) ) with time ( \(t\) ) for samples exposed to a 20 GHz microwave radiation (blue line) and when exposed a local thermal gradient (red line). ( b ) Plot of  \(O.D.\)  versus time on a log–log scale. Since both lines are approximately parallel, a Mann–Whitney U-test comparing  \(b\) -values from the separate runs showed no significant difference (Table 2 ). ( c ) Plot of the two curves shown in A after stretching in time such that the IR laser heated curve (blue line) superimposes on the microwave exposed curve (red line) with matching   \({t}_{50}\) values. ( d ) Plot of the temperature measured at the sample position using the thermographic camera. Since the IR images were recorded on the opposite side of the capillary as the IR laser used for heating, it is possible that the induced heating is not homogeneous across the capillary and its value is therefore underestimated. Both experimental protocols show a similar change in temperature with time.

Discussion and conclusions

In this work we sought to establish whether or not the application of microwave fields influences the nucleation and growth kinetics of microtubules over and above well-known effects due to heating. Tubulin is highly polar 35 and there have been several studies showing that microtubules can align in continuous or oscillating electromagnetic fields 36 , 37 , 38 , 39 including electrophoresis effects 40 , 41 . Moreover, electric field induced protein structural perturbations have been observed by time-resolved Laue diffraction 42 , albeit at several orders of magnitude higher field-strength than studied here. Conversely, structural studies of whether or not protein structural changes are induced by the application of THz electromagnetic radiation at much lower field-strengths have not always agreed 10 , 12 .

It is estimated that, on average, there are 26 arrival events and 25 departure events for every net gain of a single tubulin dimer during polymerization 43 . As such, even small perturbations that influence this kinetic balance could potentially perturb the effective forward and backward rate-constants during elongation. For example, given that microtubules align in the presence of oscillating electromagnetic fields 36 , 37 , 38 , 39 , 40 , 41 , at some point entropy perturbations might be expected to influence the polymerization kinetics. Growth assays performed during exposure to microwaves, by their very nature, involve a transient temperature change in the sample 31 , 32 . Practical considerations led us to focus on the application of microwaves in the low GHz domain, since our device for delivering microwave radiation onto samples within a quartz capillary revealed sample heating within this frequency domain 44 (Fig.  1 b). Although the observation of microwave induced heating gave confidence in the experimental design, the difference in thermal history between the experiment and controls created additional complications. Another limitation of our design is that it took approximately 7 s for samples to transit from ice to the position at which turbidity observations were recorded. It was impractical to shorten this delay by pumping faster or using tubing with a smaller inner diameter, since both these approaches induced bubbles in these viscous samples and bubbles become very problematic for turbidity measurements. Nevertheless, our use of an infrared camera during the application of microwave radiation or other perturbations allowed the temperature at the sample’s position to be monitored with time.

We observed a statistically significant effect of microwave radiation on the growth of microtubules (Fig.  3 , Table 3 ), but this effect is reproduced in experimental geometries which approximate the thermal history associated with the microwave measurements (Figs. 4 , 5 , Table 3 ). As such, we concur with the conclusion of an earlier study using 2.45 GHz microwave radiation that microwaves do not change the rate of tubulin polymerization into microtubules 20 . The maximum field-strength used in our studies (~ 2 kV/m), while considerably lower than that used in other studies of the influence of electric fields on biomolecules 36 , 39 , 42 , is eight orders of magnitude above the signal strength typically associated with mobile telephone networks (~ −60 dBm).

It is possible that our measurements were close to revealing subtle non-thermal effects of microwave radiation yet lacked statistical sensitivity. Under idealized assumptions including that the measured means and standard deviations are true, we can estimate that 200 repeats would be needed to achieve a statistical power of 0.9 for a \(p\) -value below 0.05 when comparing the effect on \(b\) -values for 166 mW of 20 GHz radiation against data recorded with an airflow generated thermal gradient across the capillary. However, for reasons of reproducibility, we performed all measurements using protein isolated from a single protein purification, and these preparations are limited to practical volumes given the available equipment. Moreover, not all datasets followed a normal distribution (Supplementary Figure S3 ), which is a standard assumption underpinning the treatment of experimental errors or sample inconsistencies. Therefore, a completely new design of the instrument utilizing smaller volumes would appear to be required to achieve an order of magnitude higher sensitivity.

There is considerable public interest in the possible existence of non-thermal effects of microwave radiation on biomolecules, due to social concerns about the influence of microwave radiation on human health as appliances operating in this frequency domain become more widely used 1 , 2 , 3 , 4 . There is also a highly-speculative literature which argues that microtubules may be able to process information by some unknown mechanism that may relate to consciousness 45 , 46 , 47 , 48 . While we consider that these ideas may inspire many to learn more about science, at some point there needs to be a connection between potentially far-reaching concepts and experimental data 49 . In the frequency domain from 3.5 to 29 GHz that we have explored in this work, there is no evidence which points towards any measurable effects on the growth of microtubules that cannot be explained as purely thermally induced.

Material and methods

Tubulin sample preparation.

Tubulin was extracted and purified from porcine brains, which were provided approximately 40 min after slaughter by Dalsjöfors Meat AB. Brains were transported from the slaughterhouse to the laboratory in ice-cold PBS (Phosphate Buffered Saline) to slow down protein degradation. The protein was purified using two cycles of polymerization-depolymerization in high molarity buffers 50 , with the addition of protease inhibitors (Protease Inhibitor cocktail, 5 ml, Sigma Aldrich) prior to the first centrifugation step. This purification protocol produces tubulin free of microtubule associated proteins (MAPs), which we confirmed using mass spectrometry. Protein solution (General Tubulin Buffer, Cytoskeleton) was divided into aliquots, flash frozen using liquid N 2 , and placed in a −80 °C freezer for storage.

UV-light scattering measurements

A microspectrophotometer 29 was used for light absorption measurements of the turbidity of microtubules under the influence of 3.5 to 29 GHz microwave radiation. Data were recorded on an Ocean Optics spectrophotometer. Tubulin polymerization was monitored by measuring the increase in absorbance at 365 nm with time through a 1 mm quartz capillary. Light transmission through the working buffer without tubulin was used as a reference. An increase in absorbance was used as a proxy to indicate the amount of tubulin within microtubules in solution 25 , 31 . Aliquots of approximately 5 μl tubulin samples were transported from ice to the region of the quartz capillary where the optical density of the sample was measured. The flow was stopped and the 5 μl aliquots were held in the same position for each measurement, and subsequently replaced for the next measurement. The entire system was constructed within an enclosed and insulated Plexiglas box which was temperature controlled by flowing hot air into the chamber. This flow was adjusted to achieve a stable temperature throughout the temperature domain (32 °C to 39 °C) over which light-scattering data were recorded. This temperature domain included the physiological temperature of a living animal, but it could not be too low otherwise the reaction kinetics became too slow to be measured accurately, and could not be too high since otherwise the initial polymerization reaction could occur during the time when the sample was being transferred from ice to the point of measurement. The sample’s temperature was monitored by using a thermocouple near the sample position and using a thermographic camera. The thermographic camera was also used to determine the temperature of the sample during exposure to 3.5 to 29 GHz fields. A delay of 7 s occurred between the sample leaving the ice bath and reaching the position at which the sample’s optical density was measured.

Exposure to electromagnetic fields

A parallel-plate waveguide-based flow-cell was purpose built to deliver AC fields onto a quartz capillary containing the sample (Fig.  1 ). The two metal plates were 64 mm long, 5 mm wide and were separated by slightly more than 1 mm, which allowed a quartz capillary sample container to fit between them. One of the plates was made of 0.30 mm thick copper and the other was integrated into the holder. The gap between the plates was supplemented with Rexolite, a polystyrene dielectric suitable for GHz applications, through which a 1 mm diameter hole was drilled to enable a free optical passthrough for the spectrophotometry measurements. A coaxial cable (Stability, Maury Microwave) fed the GHz fields from a signal generator (Anritsu MG3694C) through the waveguide, which was terminated on a 50 Ω resistor. Measurements using a thermographic camera of water heating within a quartz capillary established that there was optimal energy transfer from the AC field generator to the sample at a frequency of 20 GHz. Moreover, the thermographic camera (FLIR A600-Series) was used to identify the region where heating from the 20 GHz fields was maximal (Fig.  1 b), where a hole was drilled in the dielectric to allow an optically clear path and the sample’s optical density was recorded at this point. For the experimental runs when an electromagnetic field was applied, the signal generator was turned on for the entire duration of the measurement.

Measurements of tubulin polymerization

Measurements were carried out both with and without applied microwave fields. Because microwaves induce heating, control measurements were performed with the entire system pre-heated to the desired temperature. Three sets of measurements were made with the applied 20 GHz frequency power being nominally at source, ≤ 10 –5 mW (no field), nominally 32 mW (15 dBm, 26 mW at waveguide), nominally 80 mW (19 dBm, 66 mW at waveguide) and nominally 200 mW (23 dBm, 166 mW at waveguide), where losses in the apparatus were measured to be 0.8 dBm. The 3.5 GHz and 29 GHz measurements were performed with the highest input power only (nominally 200 mW). A thermographic camera was used to measure the sample’s temperature at the position where the sample’s optical density was measured (Fig.  1 b), which was a few degrees warmer than the surroundings when the microwave radiation was applied. The sample reached a stable temperature within seconds of arriving at the measurement spot position. After every measurement the sample was flushed, followed by washing the capillary with Milli-Q water and every new measurement began with a fresh sample.

Wave guide characterization and modelling

To facilitate comparisons between studies it has been recommended that experimental data is accompanied by computational modelling where appropriate 51 . Full wave electromagnetic simulations were run in Ansys HFSS in order to predict the electric field distribution within the sample. Representative snapshots of a single phase of the simulation shows standing wave patterns of the electromagnetic field inside the capillary (Fig.  1 e, Supplementary Figure S2 a, b). The sample was modelled as water (with dielectric properties according to the Debye model, specifically a relative permittivity of 78.4 and a dielectric loss tangent of 0.025) at room temperature (300 K), and the coaxial to parallel plate mode converter was not included in the simulation. The field distributions differ between the frequencies in the simulations and thermal line-profiles along the capillary are in keeping with the simulation results since the field intensity varies along the capillary length (Supplementary Figure S1 a). A line profile across the capillary shows that the temperature increase is slightly higher in the middle of the capillary, but the projected profile of the capillary cross section has to be taken into account, since the infrared camera will show the capillary walls in projection, which are cooled slightly due to their contact with the surrounding atmosphere (Supplementary Figure S1 b). We also measured the transmitted and reflected scattering parameters (S21 and S11) for the RF-device filled with buffer and empty using a Vector Network Analyzer (VNA, Keysight N5247A PNA-X) (Supplementary Figure S2 c–d). For these measurements, the SOLT calibration method was used, situating the calibration plane at the device interface with the coaxial cables. The S21 and S11 parameters allow us to calculate the power emission with and without sample of the waveguide and it shows that when buffer is present the emission is considerably higher (Table 1 ). The reported S values are an average around the specific frequencies (± 0.1 GHz). The difference in emission between the when the capillary was filled with sample and when it was empty suggests a large fraction of the emitted microwave power is absorbed by the sample, especially at the two higher frequencies used in this study. Simulated S21 and S11 parameters are in agreement with the measured values.

We measured the losses in the coaxial cable connecting the signal generator and the waveguide for 20 GHz at the two lower power levels to be 0.8 dBm. Our power meter (Anristu model ML2437A) could not measure above 20 dBm, but we assume that very similar losses apply for across the frequency domain used in this study since the coaxial cable and connector (K-connector) have stable characteristics over the frequency range. We therefore refer to the three different input powers into the waveguide as 26 (14.2 dBm), 66 (18.2 dBm) and 166 mW (22.2 dBm).

The conductivity measurements of the sample buffer used for the SAR estimates were made with a conductivity meter (WVR HCO 304) at room temperature (22 °C) and do not inform us about the frequency dependence of this parameter.

Control measurements using an infrared laser and airflow heating

Control measurements using other heating mechanisms were performed in a similar fashion as all measurements using microwaves. A fibre-optic cable from an IR laser (1440 nm, LuOcean P2 LU1470C Diode Laser) was positioned inside the measurement chamber such that the IR induced thermal heating profile mimicked that of the microwave heating. By adjusting the power input this could be matched to the absolute temperature change. The IR laser heated spatial profile was somewhat sharper (thermal spatial distribution ~ 3 mm, Supplementary Figure S1 a) than that measured for the microwave exposed region when samples enter the device (thermal spatial gradient ~ 7 mm, samples enter from the right in Supplementary Figure S1 a). This difference, however, is a small when compared with the length of the sample transfer lines used in this study (~ 10 cm). The essentially flat thermal spatial profiles of 3 GHz and 4 GHz in Supplementary Figure S1 a are substituted for measurements of the thermal profile when using 3.5 GHz radiation. Numerous measurements were performed using 3.5 Hz exposure and, like the 3 GHz and 4 GHz measurements, did not show any detectable heating of the sample. However, we did not save thermal spatial profiles from those measurements and these measurements could not be repeated since our thermographic camera could not be restarted when revising this manuscript. Since the polarized IR light could potentially interact with microtubules in an orientation-dependent way, another approach for applying a localized heating was devised. A flow of heated air from a hot air gun (STEINEL HG2320E) was focused and positioned so that the thermal profile (thermal spatial distribution ~ 5 mm, Supplementary Figure S1 a) also mimicked that of the microwave heating.

Data availability

The datasets generated during the current study is available from the corresponding author’s GitHub page, https://github.com/Neutze-lab .

Code availability

The custom code used to process the data and calculating statistics was implemented in MATLAB and is available from the corresponding author’s GitHub page, https://github.com/Neutze-lab .

References:

Belyaev, I. Nonthermal biological effects of microwaves: Current knowledge, further perspective, and urgent needs. Electromag. Biol. Med. 24 , 375–403 (2005).

Article   CAS   Google Scholar  

Ramundo-Orlando, A. Effects of millimeter waves radiation on cell membrane: A brief review. J Infrared Milli Terahz Waves 31 , 1400–1411 (2010).

Article   Google Scholar  

Samaras, T. et al. Potential health effects of exposure to electromagnetic fields (EMF). https://health.ec.europa.eu/publications/potential-health-effects-exposure-electromagnetic-fields-emf_en , 2015

Cotgreave, I. A. Biological stress responses to radio frequency electromagnetic radiation: are mobile phones really so (heat) shocking?. Arch Biochem Biophys 435 , 227–240. https://doi.org/10.1016/j.abb.2004.12.004 (2005).

Article   CAS   PubMed   Google Scholar  

Ziegelberger, G. et al. Guidelines for limiting exposure to electromagnetic fields (100 kHz to 300 GHz). Health Phys 118 , 483–524. https://doi.org/10.1097/HP.0000000000001210 (2020).

Frohlich, H. Biological effects of microwaves and the question of coherence. Prog Clin Biol Res 107 , 189–195 (1982).

CAS   PubMed   Google Scholar  

Pokorny, J. Excitation of vibrations in microtubules in living cells. Bioelectrochemistry 63 , 321–326. https://doi.org/10.1016/j.bioelechem.2003.09.028 (2004).

Kucera, O. & Cifra, M. Radiofrequency and microwave interactions between biomolecular systems. J Biol Phys 42 , 1–8. https://doi.org/10.1007/s10867-015-9392-1 (2016).

Article   PubMed   Google Scholar  

Foster, K. R. & Baish, J. W. Viscous damping of vibrations in microtubules. J Biol Phys 26 , 255–260. https://doi.org/10.1023/A:1010306216654 (2000).

Article   CAS   PubMed   PubMed Central   Google Scholar  

Lundholm, I. V. et al. Terahertz radiation induces non-thermal structural changes associated with Frohlich condensation in a protein crystal. Struct Dyn 2 , 054702. https://doi.org/10.1063/1.4931825 (2015).

Weissenborn, R., Diederichs, K., Welte, W., Maret, G. & Gisler, T. Non-thermal microwave effects on protein dynamics? An X-ray diffraction study on tetragonal lysozyme crystals. Acta Crystallogr D Biol Crystallogr 61 , 163–172. https://doi.org/10.1107/S0907444904030902 (2005).

Article   ADS   CAS   PubMed   Google Scholar  

Schroer, M. A. et al. Probing the existence of non-thermal Terahertz radiation induced changes of the protein solution structure. Sci Rep 11 , 22311. https://doi.org/10.1038/s41598-021-01774-6 (2021).

Article   ADS   CAS   PubMed   PubMed Central   Google Scholar  

Jelinek, F. et al. Measurement of electrical oscillations and mechanical vibrations of yeast cells membrane around 1 kHz. Electromagn Biol Med 28 , 223–232. https://doi.org/10.1080/15368370802710807[pii] (2009).

Sahu, S., Ghosh, S., Fujita, D. & Bandyopadhyay, A. Live visualizations of single isolated tubulin protein self-assembly via tunneling current: effect of electromagnetic pumping during spontaneous growth of microtubule. Sci Rep 4 , 7303. https://doi.org/10.1038/srep07303 (2014).

Sahu, S. et al. Atomic water channel controlling remarkable properties of a single brain microtubule: correlating single protein to its supramolecular assembly. Biosens Bioelectron 47 , 141–148. https://doi.org/10.1016/j.bios.2013.02.050 (2013).

Gos, P., Eicher, B., Kohli, J. & Heyer, W. D. No mutagenic or recombinogenic effects of mobile phone fields at 900 MHz detected in the yeast Saccharomyces cerevisiae. Bioelectromagnetics 21 , 515–523. https://doi.org/10.1002/1521-186X(200010)21:7%3c515::AID-BEM5%3e3.0.CO;2-K[pii] (2000).

de Pomerai, D. et al. Non-thermal heat-shock response to microwaves. Nature 405 , 417–418. https://doi.org/10.1038/35013144 (2000).

Article   ADS   PubMed   Google Scholar  

de Pomerai, D. et al. Retraction: Non-thermal heat-shock response to microwaves. Nature 440 , 437 (2006).

Google Scholar  

Buchachenko, A. Why magnetic and electromagnetic effects in biology are irreproducible and contradictory?. Bioelectromagnetics 37 , 1–13. https://doi.org/10.1002/bem.21947 (2016).

Ortner, M. J., Galvin, M. J. & Irwin, R. D. The effect of 2450-MHz microwave radiation during microtubular polymerization in vitro. Radiat Res 93 , 353–363 (1983).

Borisy, G. et al. Microtubules: 50 years on from the discovery of tubulin. Nat Rev Mol Cell Biol 17 , 322–328. https://doi.org/10.1038/nrm.2016.45 (2016).

Voter, W. A. & Erickson, H. P. The kinetics of microtubule assembly: Evidence for a two-stage nucleation mechanism. J Biol Chem 259 , 10430–10438 (1984).

Setayandeh, S. S. L. A. Influence of GHz electric fields on the mechanical properties of a microtubule. J. Mol. Model. 21 , 1–7. https://doi.org/10.1007/s00894-015-2637-x (2015).

Timmons, J. J., Preto, J., Tuszynski, J. A. & Wong, E. T. Tubulin’s response to external electric fields by molecular dynamics simulations. PLOS One 13 (2018). https://doi.org/10.1371/journal.pone.0202141

Kuchnir Fygenson, D., Flyvbjerg, H., Sneppen, K., Libchaber, A. & Leibler, S. Spontaneous nucleation of microtubules. Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 51 , 5058–5063 (1995).

CAS   Google Scholar  

Andersson, M. et al. Structural dynamics of light-driven proton pumps. Structure 17 , 1265–1275. https://doi.org/10.1016/j.str.2009.07.007 (2009).

Malmerberg, E. et al. Conformational activation of visual rhodopsin in native disc membranes. Sci Signal 8 , ra26. https://doi.org/10.1126/scisignal.2005646 (2015).

Ben Ishai, P. et al. What is the primary mover of water dynamics?. Phys. Chem. Chem. Phys. 17 , 15428–15434. https://doi.org/10.1039/C5CP01871D (2015).

Hadfield, A. & Hajdu, J. A fast and portable microspectrophotometer for protein crystallography. J. Appl. Cryst. 26 , 839–842 (1993).

Article   ADS   CAS   Google Scholar  

Santelices, I. B. et al. Response to alternating electric fields of tubulin dimers and microtubule ensembles in electrolytic solutions. Sci. Rep. https://doi.org/10.1038/s41598-017-09323-w (2017).

Article   PubMed   PubMed Central   Google Scholar  

Fygenson, D. K., Braun, E. & Libchaber, A. Phase diagram of microtubules. Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 50 , 1579–1588 (1994).

Gaskin, F., Cantor, C. R. & Shelanski, M. L. Turbidimetric studies of the in vitro assembly and disassembly of porcine neurotubules. J Mol Biol 89 , 737–755. https://doi.org/10.1016/0022-2836(74)90048-5 (1974).

B., I. & Hoaglin, D. C. Volume 16: How to Detect and Handle Outliers (1993).

Schilstra, M. J., Bayley, P. M. & Martin, S. R. The effect of solution composition on microtubule dynamic instability. Biochem J 277 (Pt 3), 839–847 (1991).

Saeidi, H. R., Lohrasebi, A. & Mahnam, K. External electric field effects on the mechanical properties of the αβ-tubulin dimer of microtubules: A molecular dynamics study. J. Mol. Modeling 20 , 1–7. https://doi.org/10.1007/s00894-014-2395-1 (2014).

Bohm, K. J., Mavromatos, N. E., Michette, A., Stracke, R. & Unger, E. Movement and alignment of microtubules in electric fields and electric-dipole-moment estimates. Electromag. Biol. Med. 24 , 319–330 (2005).

Kim, T., Kao, M. T., Hasselbrink, E. F. & Meyhofer, E. Active alignment of microtubules with electric fields. Nano Lett 7 , 211–217. https://doi.org/10.1021/nl061474k (2007).

Uppalapati, M., Huang, Y. M., Jackson, T. N. & Hancock, W. O. Microtubule alignment and manipulation using AC electrokinetics. Small 4 , 1371–1381. https://doi.org/10.1002/smll.200701088 (2008).

Ramalho, R. R., Soares, H. & Melo, L. V. Microtubule behavior under strong electromagnetic fields. Mater. Sci. Eng. C 27 , 1207–1210 (2007).

van den Heuvel, M. G., de Graaff, M. P., Lemay, S. G. & Dekker, C. Electrophoresis of individual microtubules in microchannels. Proc Natl Acad Sci USA 104 , 7770–7775. https://doi.org/10.1073/pnas.0608316104 (2007).

van den Heuvel, M. G., de Graaff, M. P. & Dekker, C. Molecular sorting by electrical steering of microtubules in kinesin-coated channels. Science 312 , 910–914. https://doi.org/10.1126/science.1124258 (2006).

Hekstra, D. R. et al. Electric-field-stimulated protein mechanics. Nature 540 , 400–405. https://doi.org/10.1038/nature20571 (2016).

Schek, H. T., Gardner, M. K., Cheng, J., Odde, D. J. & Hunt, A. J. Microtubule assembly dynamics at the nanoscale. Curr. Biol. 17 , 1445–1455 (2007).

Siege, P. H. Terahertz technology in biology and medicine. IEEE Trans. Microw. Theory Technol. 52 , 2438–2448 (2004).

Article   ADS   Google Scholar  

Craddock, T. J. A. et al. Anesthetic alterations of collective terahertz oscillations in tubulin correlate with clinical potency: Implications for anesthetic action and post-operative cognitive dysfunction. Sci Rep 7 , 1–12. https://doi.org/10.1038/s41598-017-09992-7 (2017).

Hameroff, S. & Penrose, R. Consciousness in the universe: A review of the “Orch OR” theory. Phys Life Rev 11 , 39–78. https://doi.org/10.1016/j.plrev.2013.08.002 (2014).

Craddock, T. J., Hameroff, S. R., Ayoub, A. T., Klobukowski, M. & Tuszynski, J. A. Anesthetics act in quantum channels in brain microtubules to prevent consciousness. Curr Top Med Chem 15 , 523–533. https://doi.org/10.2174/1568026615666150225104543 (2015).

Hameroff, S. R. & Watt, R. C. Information processing in microtubules. J Theor Biol 98 , 549–561. https://doi.org/10.1016/0022-5193(82)90137-0 (1982).

Kučera, O., Havelka, D. & Cifra, M. Vibrations of microtubules: Physics that has not met biology yet. Wave Motion 72 , 13–22 (2017).

Article   ADS   MathSciNet   Google Scholar  

Castoldi, M. & Popov, A. V. Purification of brain tubulin through two cycles of polymerization-depolymerization in a high-molarity buffer. Prot. Expr. Purif. 32 , 83–88. https://doi.org/10.1016/S1046-5928(03)00218-3 (2003).

Kuster, N., Schînborn, F. & Recommended minimal requirements and development guidelines for exposure setups of bio-experiments addressing the health risk concern of wireless communications. Bioelectromagnetics 21 , 508–514 (2000). https://doi.org/10.1002/1521-186X

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Acknowledgements

This work was funding primarily from the Knut and Alice Wallenberg Foundation grant KAW 2012.0275 with additional support from KAW 2012.0284, the Swedish Strategic Research Foundation (SSF SRL 10-0036) and the Swedish Research Council (Vetenskapsradet) contract 2015-00560.

Open access funding provided by University of Gothenburg. Knut och Alice Wallenbergs Stiftelse,KAW 2012.0275, Stiftelsen för Strategisk Forskning, SSF SRL 10-0036, Vetenskapsrådet, 2015-00560

Author information

These authors contributed equally: Greger Hammarin and Per Norder.

Christer Stoij is deceased.

Authors and Affiliations

Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, Sweden

Greger Hammarin, Per Norder, Rajiv Harimoorthy, Guo Chen, Peter Berntsen, Gisela Brändén & Richard Neutze

Department of Physics, Chalmers University of Technology, Gothenburg, Sweden

Guo Chen & Jan Swenson

Monash Health Imaging, Monash Health, Clayton, VIC, Australia

Peter Berntsen

Institution of Biomedicine, University of Gothenburg, Gothenburg, Sweden

Per O. Widlund

CSTechnologies, Växjö, Sweden

Christer Stoij

Department of Microtechnology and Nanoscience, Chalmers University of Technology, Gothenburg, Sweden

Helena Rodilla

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Contributions

RN, GB, GH, PN, RH, GC and JS designed research. C.S. designed and built the device for delivering microwaves. GB, PN and GH isolated and purified active tubulin. GB, PN, GH and GC performed light-scattering measurements. CS and HR contributed analytic tools. GH, PN, RH, GC, POW and RN analysed data. GH, PN, RH and RN wrote the manuscript.

Corresponding author

Correspondence to Richard Neutze .

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Hammarin, G., Norder, P., Harimoorthy, R. et al. No observable non-thermal effect of microwave radiation on the growth of microtubules. Sci Rep 14 , 18286 (2024). https://doi.org/10.1038/s41598-024-68852-3

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MythBusters Episode 212: DO Try This at Home?

Premier Date: February 1, 2014

This episode involved several myths that viewers might be able to try at home.

Water that has been boiled in a microwave oven will kill plants.

busted , do try at home

Adam built a tray to hold four pairs of romaine lettuce plants, each receiving a different type of water: microwave-boiled, stove-boiled, unheated from the tap, and no water at all. The two boiled samples were cooled to room temperature before being used. All plants received the same amounts of water and light for one week. At the end of this time, Adam found that the plants given microwave-boiled water had grown larger than all the others, and that the ones given no water had died.

The wake from a sharply turning jet boat can put out a fire on a stationary boat. (Based on a viral video.)

confirmed , don’t try at home

The Build Team borrowed a jet boat, and Tory practiced getting it up to speed and doing a sharp 180-degree turn. They loaded a wooden pallet of hay onto a second boat and set it on fire. With Grant and the boat’s owner on board, Tory drove toward the burning boat at 50 miles per hour (80 km/h) and cut a sharp turn, covering the burning boat with a substantial spray of water. The first pass put out the flames, but smoke was still billowing from the hay. Two more passes were made to positively extinguish the fire.

A large number of metronomes placed on a sliding platform will perfectly synchronize.

Adam demonstrated that a single metronome on a sliding platform would slightly shake the platform back and forth. He set a lightweight platform on top of two lengths of pipe to act as rollers, and was able to get 2, 5, and 11 metronomes to synchronize. He and Jamie then set up 216 metronomes on foam board which was floating on an air hockey table. During 30 minutes of ticking, only smaller groups of the metronomes fell into and out of sync. Adam commented that variations in manufacturing tolerances would make it nearly impossible to synchronize such a large number of metronomes.

Chrome ball-chain can appear to levitate briefly as it falls out of a container.

confirmed , do try at home

Jamie placed a beaker filled with one long piece of chain on a counter and pulled one end sharply up over the edge to start it falling. High-speed camera footage revealed that the balls did follow the arc of that initial pull, and tests with larger balls and from greater heights increased the effect. He explained that the effect may have been due to the combination of inertia from the pull, the chain’s own weight, and the low friction due to the slick surfaces.

Demonstrations of the classroom science experiment known as “elephant toothpaste.”

only try first version at home

Kari mixed household hydrogen peroxide solution, liquid dish soap, and food coloring in a graduated cylinder, then added a small amount of yeast. The peroxide decomposed into water and oxygen gas, causing the soap to foam up and out of the container.

Kari repeated the experiment, using a concentrated laboratory-grade peroxide solution and potassium iodide instead of yeast. This test generated a large volume of hot foam and steam, and was deemed unsafe for the home. In a final test, described as “Monster Toothpaste”, the Build Team scaled up the recipe by a factor of 200. When the chemicals were mixed, they generated a massive eruption of foam.

Demonstration of a chemical reaction with results resembling a black snake firework, but occurring much more quickly.

don’t try at home

Grant first mixed sugar and sulfuric acid. The sugar decomposed to form steam and carbon residue, but the reaction did not appear to be particularly fast or violent. When he switched the sugar for an unnamed organic compound and heated the mixture for several seconds, it generated an instantaneous burst of smoke and a tall column of carbon. He stressed that the use of sulfuric acid made this reaction dangerous.

Investigating the dangers involved in using a dry ice bomb.

Adam set up a rig to screw caps onto bottles using a power drill. At the bomb range, he placed a bottle in a frame and added dry ice and water, with pressure sensors arranged around it, then retreated to a safe distance and triggered the drill to put on the cap. The explosion of a 350-ml (12 fl oz) bottle registered a maximum pressure of 3 pounds per square inch (21 kPa); however, Adam and Jamie discovered that one of the frame’s steel supports had fractured and bent.

A 2-liter bottle bulged out greatly before exploding and gave a maximum of 7 pounds per square inch (48 kPa), enough to cause permanent hearing damage. When Adam and Jamie repeated the test with the bottle held in a set of rubber and bone forearms made by Jamie, the blast inflicted several lacerations, fractures, and wounds from embedded shrapnel.

Water falling in front of a stereo speaker can appear to freeze in place.

Tory set up a pipe to dribble water in front of a speaker and filmed the setup with a video camera, adjusting the output frequency to affect the vibration of the water in midair. Near 24 Hertz, the water seemed to fall very slowly; Tory pointed out that the effect was an optical illusion, caused by the vibration being nearly synchronized with the camera’s filming rate of 24 frames per second. At frequencies below 24 Hertz, the effect made the water appear to rise back toward the pipe.

Previous: Episode 211: Car Chase Chaos / Animal Antics

Next: Episode 213: Mythssion Impossible

Exploding Water in the Microwave

Did you know that heating water in the microwave can be dangerous.

Print this Experiment

Did you know that heating water in the microwave can actually be dangerous? This is not an experiment, but rather a warning to help you avoid a potential disaster. The American Burn Association (ABA) has identified scald burns from superheated liquids in microwaves as a target for a new public awareness campaign… “Water alone should never be heated in a microwave.” Here’s why…

This is an all too common example of what can happen. A man decided to have a cup of instant coffee, so he heated a cup of water in the microwave. When the timer went off, he removed the cup from the microwave and noticed that the water had not boiled.

Just then, the water literally “blew up” in his face. His whole face was blistered with first and second degree burns, which left some permanent scarring and damage to his left eye. While at the hospital, the doctor attending him stated that his is a fairly common occurrence. Water (alone) should never be heated in a microwave oven.

Why? This phenomenon is known as superheating. It can occur anytime water is heated – especially if the cup or bowl is new. What happens is that the water heats faster than the vapor bubbles can form. If the cup is very new, then it is unlikely to have small surface scratches in it that provide a place for the bubbles to form (called nucleation sites).

Without bubbles, the water cannot release the heat that has built up, the liquid does not boil, and it continues to heat up past its boiling point. If the water is bumped or jarred, it’s enough of a shock to cause the bubbles to rapidly form and the result is an exploding liquid that is scalding hot. One solution is to place a wooden stir stick or something non-metallic in the water to help diffuse the energy as it is heating in the microwave.

Dr. Gordon Lindberg, MD, PhD, and director of the burn unit at University of Colorado Health Sciences Center, agrees that the phenomenon of superheated liquids is a real problem. According to Dr. Lindberg, the American Burn Association (ABA) has identified scald burns from superheated liquids in microwaves as a target for a new public awareness campaign.

“These burns are dramatic and traumatic because they often affect the face and hands of the burn victim. Fortunately, these burns rarely need grafting; however, they are extremely painful and in children these burns often lead to hospitalization for wound care and pain control.

The best way to avoid these burns is to place a wooden coffee stirrer in the liquid when heating it and also to let all heated liquids cool for a few minutes inside the microwave before removing them.”

If you receive one of these burns, and especially if it covers the face or hands, seek a burn care specialist for care. Initial treatment for the burn can be performed in an ED or at a doctor’s office, but a burn specialist should see the burn within 24-48 hours after the injury, especially if the face is involved. If the eyes are involved, an ophthalmologist should be consulted immediately.

Browse more experiments by concept:

ORIGINAL RESEARCH article

The microwave bacteriome: biodiversity of domestic and laboratory microwave ovens.

• 1 Institute for Integrative Systems Biology (I2SysBio), University of Valencia-CSIC, Valencia, Spain
• 2 Darwin Bioprospecting Excellence S.L., Valencia, Spain

Microwaves have become an essential part of the modern kitchen, but their potential as a reservoir for bacterial colonization and the microbial composition within them remain largely unexplored. In this study, we investigated the bacterial communities in microwave ovens and compared the microbial composition of domestic microwaves, microwaves used in shared large spaces, and laboratory microwaves, using next-generation sequencing and culturing techniques. The microwave oven bacterial population was dominated by Proteobacteria , Firmicutes , Actinobacteria , and Bacteroidetes , similar to the bacterial composition of human skin. Comparison with other environments revealed that the bacterial composition of domestic microwaves was similar to that of kitchen surfaces, whereas laboratory microwaves had a higher abundance of taxa known for their ability to withstand microwave radiation, high temperatures and desiccation. These results suggest that different selective pressures, such as human contact, nutrient availability and radiation levels, may explain the differences observed between domestic and laboratory microwaves. Overall, this study provides valuable insights into microwave ovens bacterial communities and their potential biotechnological applications.

1 Introduction

Microorganisms that thrive in ecosystems characterized by extreme environmental conditions have been well studied to elucidate the evolutionary mechanisms that have favored their adaptation. Natural extreme environments represent an exceptional source of novel microbial species, as well as a source of novel secondary metabolites with biotechnological applications ( Shu and Huang, 2022 ). However, one does not need to travel that far in search for extreme environments.

As a result of human activity and modernization, many different man-made artificial devices were built in the last century. Many studies have described the microbial populations present in highly anthropized artificial environments such as elevator buttons ( Kandel et al., 2014 ), the underground ( Gohli et al., 2019 ), and small electronic devices ( Lax et al., 2015 ). Other works have unveiled that some man-made devices, machines, and appliances, despite being in constant contact with humans or human activities, have their own microecosystems with their own selective pressures and conserved microbiomes. This is the case, for example, of coffee machines ( Vilanova et al., 2015 ) or dishwashers ( Raghupathi et al., 2018 ).

Microwave irradiation has been used for decades to reduce the presence of microorganisms in food and extend food shelf life. The application of an electromagnetic wave in the range of 300 MHz to 300 GHz to a dielectric medium such as food, also known as microwave heating, generates heat to reach lethal temperatures that inactivate most microorganisms, such as Escherichia coli , Enterococcus faecalis , Clostridium perfringens , Staphylococcus aureus , Salmonella spp. and Listeria spp. ( Woo et al., 2000 ; Kubo et al., 2020 ). Recent work has shown that cell inactivation is associated with deactivation of oxidation-regulating genes, DNA damage and increased permeability and disrupted integrity of cell membranes ( Cao et al., 2018 ; Shaw et al., 2021 ). Despite this extensive characterization of the biological effects of microwave radiation on foodborne bacteria, to our knowledge there are no reports of microwaves as microbial niches, that is, environments where specific selective pressures (in this case, thermal shock, microwave radiation, and desiccation) can shape a specifically adapted microbiome.

In the present work, we describe the bacterial composition of 30 microwaves from different environments (domestic, domestic of shared use, and laboratory) to explore the intricacies of the microwave microbiome, with a particular focus on identifying variations based on usage patterns. The goal is to determine whether microwaves harbor a distinct microbiome shaped by prolonged exposure to microwave radiation, or whether their bacterial communities are influenced by food interactions and user habits.

2.1 Strain collection

Thirty microwave ovens (10 from domestic use, 10 of domestic shared-use, and 10 of laboratory use) were sampled and used to culture microbial strains on Columbia agar, TSA, YM, R2A, and NA. This yielded a collection of 101 isolates dominated by strains belonging to the genera Bacillus , Micrococcus , and Staphylococcus , followed by Brachybacterium , Paracoccus , and Priestia . Members of the genera Acinetobacter , Bhargavaea , Brevibacterium , Brevundimonas , Dermacoccus , Klebsiella , Pantoea , Pseudoxanthomonas , and Rhizobium were found only in domestic microwaves. Strains belonging to the genera Arthrobacter , Enterobacter , Janibacter , Methylobacterium , Neobacillus , Nocardioides , Novosphingobium , Paenibacillus , Peribacillus , Planococcus , Rothia , Sporosarcina , and Terribacillus were isolated only in microwaves of domestic-shared use. A strain of Nonomuraea species was isolated only in laboratory microwaves ( Figure 1 ).

Figure 1 . Main bacterial genera isolated from domestic, domestic-shared and laboratory microwaves.

Moreover, microbial strains of the genera Bacillus , Curtobacterium , Prolinoborus , Pseudomonas , and Staphylococus were isolated from both domestic and domestic-shared microwaves. Kocuria and Moraxella strains were obtained from domestic-shared and laboratory microwaves. Members of four genera were found in all types of microwaves: Brachybacterium , Micrococcus , Paracoccus , and Priestia ( Figure 1 ).

2.2 Analysis of bacterial diversity of microwaves by NGS

NGS (Next Generation Sequencing) analysis of the conserved V3 and V4 regions of the 16S rRNA gene allowed the exploration of bacterial diversity within microwave ovens. The results showed that, at the phylum level, Proteobacteria predominated in microwave bacterial communities, followed by Firmicutes and Actinobacteria to a lesser extent ( Figure 2 ; Supplementary file S1 ). Differential abundance analysis confirmed the higher presence of the phyla Chloroflexi , Acidobacteria , Deinococcus-Thermus , and Cyanobacteria in the laboratory microwaves compared to the household microwaves ( Supplementary file S2 ). The latter phylum was also more abundant in the domestic-shared microwave group compared to the domestic (not shared) microwaves.

Figure 2 . Taxonomic distribution at the phylum level of the bacteria present in the three types of microwaves: laboratory (M1–M10), domestic (M11–M20), and domestic-shared (M21–M34).

At the genus level, laboratory microwaves showed a more homogeneous composition than domestic microwaves ( Figure 3 ). Acinetobacter , Pseudomonas , and Sphingobium were present in all types of microwaves. Among the significantly more abundant genera in laboratory microwaves compared to household microwaves were Delftia , Micrococcus , Deinocococcus , and an unidentified genus of the phylum Cyanobacteria ( Supplementary file S2 ). The opposite trend was observed for the genera Epilithonimonas , Klebsiella , Shewanella , and Aeromonas , among others. In addition, differential abundance analysis between domestic and domestic-shared microwaves showed that two genera, Lawsonella and Methyloversatilis , were significantly more abundant in the latter group. When comparing NGS results with the culturing techniques, it was found that almost all of the isolated genera were detected by 16S rRNA gene sequencing. Interestingly, Bhargavaea , Janibacter , and Nonomuraea , which could be cultured, were not detected by sequencing.

Figure 3 . Taxonomic distribution at the genus level of the bacteria present in the three types of microwaves: laboratory (M1–M10), domestic (M11–M20), and domestic-shared (M21–M34).

In terms of alpha diversity analysis, domestic microwaves had the lowest number of distinct ASVs detected and also lower Shannon index values, although these trends were only significant when comparing this type of sample with laboratory microwaves ( Figure 4 ). No significant differences were found between domestic and domestic-shared microwaves, nor between the latter and laboratory microwaves, in the number of distinct ASVs observed, Shannon index and Simpson index. Overall, between 100 and 300 different ASVs were detected, depending on the type of sample, as well as Shannon indices below 4 in household microwaves and above in laboratory microwaves, while Simpson indices ranged from 0.8 to 1.

Figure 4 . Alpha diversity results (richness or number of ASVs, Shannon index and Simpson index) for the three types of microwaves: laboratory (M1–M10), domestic (M11–M20), and domestic-shared (M21–M34).

At the β-diversity level, when comparing the different groups of samples at a qualitative and quantitative level, it was observed that they were statistically different from each other (PERMANOVA test, p -value < 0.05). Laboratory samples grouped closely together, indicating a greater homogeneity in their bacterial composition ( Figure 5 ). When comparing household microwaves, samples tended to cluster within each of the two groups (domestic and shared-domestic), although this was less evident than with laboratory microwaves. Furthermore, the β-diversity of the microwave samples was also compared with that of two highly irradiated, extreme environments: solar panels and nuclear waste samples; as well as an anthropized indoor environment: kitchen surfaces ( Figure 6 ). The samples were grouped according to their origin, although the solar panel samples and especially the kitchen samples appeared to display a more similar bacterial composition to the household microwave samples. The nuclear waste disposal samples showed the least similarity to the microwave samples.

Figure 5 . Beta diversity (PCoA) based on Bray–Curtis (ASV level) for the three types of microwaves: laboratory (M1–M10), domestic (M11–M20), and domestic-shared (M21–M34).

Figure 6 . Beta diversity (PCoA) based on Bray–Curtis (ASV level) for the three types of microwaves: laboratory (M1–M10), domestic (M11–M20), and domestic-shared (M21–M34) and samples from other studies: four kitchen samples, four samples from solar panels and six from nuclear waste.

3 Discussion

In this study, we describe the bacterial communities of microwaves by NGS and compare the results obtained in domestic microwaves, domestic use microwaves located in large shared spaces, and laboratory microwaves. In parallel, this work was complemented with the isolation of culturable microorganisms from the same samples.

Through culturing techniques, we found that many of the isolated strains belonged to typically commensal and anthropic genera such as Bacillus , Micrococcus , Staphylococcus , Micrococcus , and Brachybacterium ( Moskovicz et al., 2021 ; Skowron et al., 2021 ; Boxberger et al., 2022 ). As might be expected, human skin-related microorganisms are often found on artificial devices with which humans have frequent contact ( Fujiyoshi et al., 2017 ). In addition, strains belonging to genera potentially pathogenic to humans, such as Klebsiella or Brevundimonas , were identified in some samples ( Podschun and Ullmann, 1998 ; Ryan and Pembroke, 2018 ). Although these genera are less common on the skin, they can be found in the human microbiome on mucosal surfaces ( Paczosa and Mecsas, 2016 ; Leung et al., 2019 ).

Analysis of the 16S rRNA gene revealed that the bacterial communities of the microwaves were dominated by members of the phyla Proteobacteria , Firmicutes , Actinobacteria , and Bacteroidetes , which also correspond to the predominant phyla in the human skin microbiome ( Cho and Blaser, 2012 ), serving as an indicator of microwave anthropization. In this regard, the relevant presence of taxa that can be found in human skin such as Acinetobacter , Pseudomonas , Moraxella, Bacillus , and Staphylococcus ( Kumar et al., 2019 ) was also detected at the genus level. Despite the similarities found between the samples due to the frequent use of microwaves by humans, differences were also detected between the three types of microwaves, especially between laboratory and domestic microwaves. In the latter, an enrichment of food-associated genera was anticipated due to their primary culinary application. Consequently, it was logical to observe more abundant genera such as Shewanella , Enterobacter , Aeromonas , Lactococcus , or Klebsiella in this type of microwaves, as they are frequently detected in food matrices and food-related habitats, typically associated with degradation or spoilage processes ( Jarvis et al., 2018 ). It is important to note that certain species belonging to some of these genera, such as A. hydrophila , K. pneumoniae , and E. cloacae , are common contaminants in various food-related habitats and they pose potential health risks due to their pathogenic properties and antibiotic resistance ( Daskalov, 2006 ; Shaker et al., 2007 ; Rodrigues et al., 2022 ). Their presence in the microwaves, as well as on other surfaces in the built environment, suggests the importance of regular cleaning practices to mitigate potential health risks, as frequent and adequate cleaning with appropriate disinfectants helps to prevent the presence of pathogens associated with these domestic environments ( Carstens et al., 2022 ). As for laboratory microwaves, their use is completely different, as they are never used to heat food, but mainly to heat aqueous solutions, biological samples, synthetic materials or chemical reagents. Since food cannot be a shaping factor of their microbiomes, we hypothesize that the primary factor determining the microbiome in laboratory microwaves is the extreme conditions created within them (with heating processes that often require longer exposure times). In fact, some of the genera that were significantly more abundant in this group of samples included species known for their resistance to high doses of radiation, such as Deinococcus , Hymenobacter , Kineococcus , Sphingomonas , and Cellulomonas ( Nayak et al., 2021 ). Some of the mechanisms used by bacteria to withstand such adverse conditions include expression of heat shock proteins (HSPs) ( Maleki et al., 2016 ) and antioxidant enzymes ( Munteanu et al., 2015 ), maintenance of cell integrity through changes in membrane fatty acid composition ( Chen and Gänzle, 2016 ), biofilm formation ( Bogino et al., 2013 ), or DNA repair ( Sghaier et al., 2008 ). In particular, Deinococcus species such as D. radiodurans and D. geothermalis are known for their ability to withstand extreme environmental conditions such as ionizing radiation, desiccation, or high temperatures due to their highly efficient DNA repair mechanisms and protective cellular components ( Mattimore and Battista, 1996 ; Liedert et al., 2012 ). Moreover, a previous study by Shen et al. (2020) showed that Acidovorax and Aquabacterium , two other genera enriched in laboratory samples, were differentially more abundant than others at higher temperatures. The phylum Cyanobacteria and Chloroflexi , which were also more common in laboratory microwaves, have also been described as extremophiles that can withstand environments with high levels of radiation and temperature ( Lacap et al., 2011 ; Uribe-Lorío et al., 2019 ). The greater presence of bacteria resistant to these types of selective pressures could explain the higher alpha diversity values found in laboratory versus domestic microwaves. In addition, the more frequent use of domestic-shared microwaves and by more people could also favor greater diversity in this group with respect to domestic microwaves, as seen in other devices like washing machines ( Jacksch et al., 2021 ).

In addition, when the bacterial communities of microwaves were compared with those of other highly irradiated environments—solar panels and nuclear waste residues—and kitchens (food-related habitats in constant contact with humans), it was found that domestic microwaves were more similar to kitchen surface samples. However, laboratory microwaves appeared to have similarities to kitchen and, to a lesser extent, solar panel samples. Thus, genera such as Acinetobacter , Pseudomonas , Bacillus , and Staphylococcus , widely present in the vast majority of microwaves analyzed, are typical of kitchens ( Speirs et al., 1995 ; Malta et al., 2020 ). Interestingly, many of the genera significantly more present in laboratory microwaves (such as Deinococcus , Hymenobacter , Sphingomonas , Ralstonia , or Micrococcus ) are typically identified in solar panels ( Porcar et al., 2018 ; Tanner et al., 2018 , 2020 ). These results confirm that all microwave samples resembled each other, although the laboratory microwaves showed greater similarities with microbiomes from environments with relatively low organic matter and subjected to intense radiation or desiccation.

Further work is needed to study the microbial adaptations of strains isolated from microwaves to high temperatures, desiccation, and electromagnetic radiation. For example, although the ability of bacteria to tolerate high temperatures can greatly vary depending on species and strains, those present in higher abundance in microwaves - Acinetobacter , Pseudomonas , Delftia , Bacillus , and Sphingobium - are known to exhibit a range of tolerance to high temperatures, where Acinetobacter has been reported to tolerate up to 50°C ( Hrenovic et al., 2014 ), Pseudomonas up to 45°C ( Silby et al., 2009 ), Delftia up to 40°C ( Roy and Roy, 2019 ), Bacillus up to 80°C ( Thomas, 2012 ) and Sphingobium up to 40°C ( Singh et al., 2023 ). Some strains of Acinetobacter and Pseudomonas have been found to survive for extended periods of time in dry environments, including hospital surfaces ( Espinal et al., 2012 ) and air filters (Pinna et al., 2009) respectively, while Bacillus species are well-known for their ability to form spores that can survive in a desiccated state for many years ( Checinska et al., 2015 ). Similarly, some species of Sphingobium have been found to survive in dry soil and sediment environments ( Madueño et al., 2018 ).

4 Conclusion

Three types of microwaves were studied in order to shed light on their bacterial communities. Our findings revealed the intricate interplay between microwave radiation exposure, food interactions, and user habits in shaping the bacteriome of microwaves. The distinct microbial composition observed between laboratory and household microwaves underscored the influence of usage patterns on microbial communities. Household microwaves, enriched in food-associated genera, reflected their primary culinary use, while laboratory microwaves harbored radiation-, desiccation-, and high-temperature-resistant taxa, indicating prolonged exposure to microwave radiation and suggesting a selective pressure of such harsh factors in shaping the distinctive microbial profile we found. However, more research is needed to understand how certain bacterial strains commonly found in microwaves adapt to these selective pressures. Indeed, this analysis could provide relevant information regarding the biotechnological potential of the microwave bacteriome.

5 Experimental procedures

5.1 sampling.

The inner cubicle of 10 domestic, 10 shared-domestic and 10 laboratory microwaves was sampled by rubbing a sterile collection swab humidified with Phosphate Buffer Saline solution (PBS, composition in g l-1: NaCl; 8.0, KCl; 2.0, Na 2 HPO 4 ; 1.44, KH 2 PO 4 ; 0.24. pH; 7.4) that was stored in Eppendorf tubes containing 500 μL PBS and transported to the laboratory at ambient temperature (20–25°C). Samples were immediately used for strain isolation and stored at −20°C until genomic DNA was extracted. A detailed list of the samples taken, and the corresponding microwaves characteristics can be found in Supplementary Table S1 .

5.2 Strain isolation and identification

For bacterial isolation through culturing techniques, five different growth media were used in this study: Nutrient Agar (NA, composition in g/L: peptone 5, meat extract 3, NaCl 5, agar 15, pH 7.2), Reasoner’s 2A agar (R2A, composition in g/L: peptone 1, yeast extract 0.5, dextrose 0.5, soluble starch 0.5, K 2 HPO 4 0.3, MgSO 4 0.05, sodium pyruvate 0.3, 15 agar, pH 7.2), Trypticase Soy Agar medium (TSA, contained in g/L: tryptone 15, soya peptone 5, NaCl 5, agar 15, pH 7.2), Yeast Mold Agar medium (YM, contained in g/L: yeast extract 3, malt extract 3, dextrose 10, peptone soybean 4, agar 15, pH; 6.2), Columbia Blood Agar medium (CBA, contained in g/L: special peptone 23, starch 1, NaCl 5, agar 10, pH 7.3).

Samples were homogenized in Eppendorf tubes by vigorously mixing with a vortex, and serial dilutions were plated on the media above and incubated at room temperature for 7 days. After 1 week of incubation, individual colonies were selected and isolated by re-streaking onto fresh medium. Pure cultures were cryo-preserved at −80°C in 15% glycerol.

For the taxonomic identification of the strains, PCRs amplifying a fragment of the 16S rRNA gene were carried out using the universal primers 8F (5′-AGA GTT TGA TCC TGG CTC AG-3′) and 1492R (5′-CGG TTA CCT TGT TAC GAC TT-3′) after extracting the DNA by boiling the cells at 99°C for 10 min in MilliQ-water. The 16S rRNA PCR was performed using the NZYTaq II 2× Green Master Mix, and the following PCR cycle: initial denaturation at 95°C for 3 min; 30 cycles of amplification (15 s at 94°C, 15 s at 50°C, 50 s at 72°C); and 2 min of extension at 72°C. The PCR products were checked by electrophoresis in a 1.2% agarose gel and subsequently precipitated overnight in isopropanol 1:1 (vol:vol) and potassium acetate 1:10 (vol:vol; 3 M, pH 5). DNA pellets were washed with 70% ethanol, resuspended in 15 μL Milli-Q water and Sanger sequenced by Eurofins Genomics (Germany). All the sequences were manually trimmed before comparing them against the EzBioCloud 1 and NCBI online databases. 2 EzBioCloud was used to taxonomically identify the closest type strains.

5.3 Isolation of genomic DNA

Genomic DNA was isolated from the samples using the PowerSoil DNA Isolation kit (MO BIO laboratories, Carlsbad, CA, United States) following the manufacturer’s instructions and quantified using the Qubit dsDNA HS Assay kit (Qubit 2.0 Fluorometer, Q32866). Three DNA extractions of new, unused sterile collection swabs humidified with PBS solution were also carried out, one of them together with the microwave’s samples and the remaining two on different subsequent days. These two later ones were sent for high-throughput rRNA sequencing separately in two other sequencing batches with samples belonging to other projects.

5.4 High-throughput rRNA sequencing and metataxonomic analysis

In order to study the bacterial communities present in the microwaves, the extracted genomic DNA was used to amplify the hypervariable region V3-V4 of the 16S ribosomal RNA gene. The conserved regions V3 and V4 (459 bp) of the 16S rRNA gene were amplified using the following forward and reverse primers: 5′-TCG TCG GCA GCG TCA GAT GTG TAT AAG AGA CAG CCT ACG GGN GGC WGC AG 3′ and 5′-GTC TCG TGG GCT CGG AGA TGT GTA TAA GAG ACA GGA CTA CHV GGG TAT CTA ATC C-3′, and the following PCR cycle: initial denaturation at 95°C for 3 min; 25 cycles of amplification (30 s at 95°C, 30 s at 55°C, 30 s at 72°C); and 5 min of extension at 72°C ( Satari et al., 2020 ). The amplification was carried out using the KAPA HiFi HotStart ReadyMix PCR kit (KK2602). The 16S rRNA amplicons were mixed with Illumina sequencing barcoded adaptors (Nextera XT index kit v2, FC-131-2001), and libraries were normalized and merged. The pools with indexed amplicons were loaded onto the MiSeq reagent cartridge v3 (MS-102-3003) and spiked with 10% PhiX control to improve the sequencing quality, that was finally conducted using paired-ends on an Illumina MiSeq platform (2 × 300 bp) in the Foundation for the Promotion of Health and Biomedical Research of the Valencian Community (Fisabio) (Valencia, Spain).

The raw Illumina sequences were loaded into Qiime2 (v2021.2.0) ( Bolyen et al., 2019 ). The quality of the sequences was checked using the plugin Demux and the Qiime2-integrated DADA2 pipeline was used for trimming and joining the sequences, removing chimeras and detecting amplicon sequence variants (ASVs) (>99.9% of similarity). The taxonomy of each sequence variant was determined via the classify-Sklearn module from the feature-classifier plugin, employing Greengenes-SILVA-RDP (GSR) ( Molano et al., 2024 ) as reference database for the 16S rRNA taxonomic assignment (V3-V4 hypervariable region). Results were analyzed and plotted with the phyloseq R package (v. 1.30.0) ( McMurdie and Holmes, 2013 ) and ggplot2 (v3.4.0).

The beta diversity analysis was carried out using the principal component analysis (PCoA) after calculating the distances between samples using the Bray-Curtis method, using phyloseq R package (v. 1.22.3) ( McMurdie and Holmes, 2013 ) with Bray–Curtis dissimilarities. PERMANOVA tests were calculated with vegan using the adonis2 function from the vegan R package (v2.6.4) to detect statistically significant differences in the composition of the microbiome between the groups analyzed. The differential abundance analyses between taxa were conducted using the MaAsLin2 R package (v1.0.0) (Mallick et al., 2021) with the following parameters: min_abundance = 0.01, min_prevalence = 0.33, max_significance = 0.05, normalization = “None,” transform = “LOG,” analysis_method = “LM,” correction = “BH,” standardize = FALSE. Differentially abundant taxa were considered significant if the adjusted p -value was less than or equal to 0.05.

Additionally, the bacterial profile obtained in terms of β-diversity was compared with two extreme environments with high levels of radiation: solar panels and nuclear waste samples, along with a human-modified indoor environment represented by kitchen samples ( Supplementary Table S2 ). For this purpose, publicly available datasets were downloaded from NCBI.

Data availability statement

Raw reads of the samples analyzed in this study are available at NCBI’s Sequence Read Archive (SRA) (Bioproject Accession PRJNA977132).

Author contributions

AI: Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Supervision, Validation, Visualization, Writing – original draft, Writing – review & editing. LM: Data curation, Formal analysis, Investigation, Methodology, Writing – review & editing. DT: Data curation, Formal analysis, Investigation, Methodology, Visualization, Writing – original draft, Writing – review & editing. MP: Conceptualization, Funding acquisition, Investigation, Project administration, Resources, Supervision, Validation, Writing – original draft, Writing – review & editing.

The author(s) declare that financial support was received for the research, authorship, and/or publication of this article. Financial support from the European Union H2020 (MIPLACE project ref. PCI2019-111845-2, Natural and Synthetic Microbial Communities for Sustainable Production of Optimised Biogas, MICRO4BIOGAS, Grant agreement ID: 101000470) and the Agencia Estatal de Investigación (AEI) (427 Programación Conjunta Internacional 2019) is acknowledged.

Conflict of interest

DT and MP were employed by Darwin Bioprospecting Excellence S.L.

The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Publisher’s note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

Supplementary material

The Supplementary material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fmicb.2024.1395751/full#supplementary-material

1. ^ https://www.ezbiocloud.net

2. ^ https://blast.ncbi.nlm.nih.gov/Blast.cgi

Bogino, P., Abod, A., Nievas, F., and Giordano, W. (2013). Water-limiting conditions alter the structure and biofilm-forming ability of bacterial multispecies communities in the alfalfa rhizosphere. PLoS One 8:e79614. doi: 10.1371/journal.pone.0079614

PubMed Abstract | Crossref Full Text | Google Scholar

Bolyen, E., Rideout, J. R., Dillon, M. R., Bokulich, N. A., Abnet, C. C., Al-Ghalith, G. A., et al. (2019). Reproducible, interactive, scalable and extensible microbiome data science using QIIME 2. Nat. Biotechnol. 37, 852–857. doi: 10.1038/s41587-019-0209-9

Crossref Full Text | Google Scholar

Boxberger, M., Magnien, S., Antezack, A., Rolland, C., Makoa, M., La-Scola, B., et al. (2022). Brachybacterium epidermidis Sp. Nov., a novel bacterial species isolated from the Back of the right hand, in a 67-year-old healthy woman. Int. J. Microbiol. 2022, 2875994–2875998. doi: 10.1155/2022/2875994

Cao, J.-X., Wang, F., Li, X., Sun, Y.-Y., Wang, Y., Ou, C.-R., et al. (2018). The influence of microwave sterilization on the ultrastructure, permeability of cell membrane and expression of proteins of Bacillus Cereus . Front. Microbiol. 9:1870. doi: 10.3389/fmicb.2018.01870

Carstens, C. K., Salazar, J. K., Sharma, S. V., Chan, W., and Darkoh, C. (2022). Evaluation of the kitchen microbiome and food safety behaviors of predominantly low-income families. Front. Microbiol. 13:987925. doi: 10.3389/fmicb.2022.987925

Checinska, A., Paszczynski, A., and Burbank, M. (2015). Bacillus and other spore-forming genera: variations in responses and mechanisms for survival. Annu. Rev. Food Sci. Technol. 6, 351–369. doi: 10.1146/annurev-food-030713-092332

Chen, Y. Y., and Gänzle, M. G. (2016). Influence of cyclopropane fatty acids on heat, high pressure, acid and oxidative resistance in Escherichia coli . Int. J. Food Microbiol. 222, 16–22. doi: 10.1016/j.ijfoodmicro.2016.01.017

Cho, I., and Blaser, M. J. (2012). The human microbiome: at the interface of health and disease. Nat. Rev. Genet. 13, 260–270. doi: 10.1038/nrg3182

Daskalov, H. (2006). The importance of Aeromonas hydrophila in food safety. Food Control 17, 474–483. doi: 10.1016/j.foodcont.2005.02.009

Espinal, P., Martí, S., and Vila, J. (2012). Effect of biofilm formation on the survival of Acinetobacter baumannii on dry surfaces. J. Hosp. Infect. 80, 56–60. doi: 10.1016/j.jhin.2011.08.013

Fujiyoshi, S., Tanaka, D., and Maruyama, F. (2017). Transmission of airborne Bacteria across built environments and its measurement standards: a review. Front. Microbiol. 8:2336. doi: 10.3389/fmicb.2017.02336

Gohli, J., Bøifot, K. O., Moen, L. V., Pastuszek, P., Skogan, G., Udekwu, K. I., et al. (2019). The subway microbiome: seasonal dynamics and direct comparison of air and surface bacterial communities. Microbiome 7:160. doi: 10.1186/s40168-019-0772-9

Hrenovic, J., Durn, G., Goic-Barisic, I., and Kovacic, A. (2014). Occurrence of an environmental Acinetobacter baumannii strain similar to a clinical isolate in Paleosol from Croatia. Appl. Environ. Microbiol. 80, 2860–2866. doi: 10.1128/AEM.00312-14

Jacksch, S., Zohra, H., Weide, M., Schnell, S., and Egert, M. (2021). Cultivation-based quantification and identification of Bacteria at two hygienic key sides of domestic washing machines. Microorganisms 9:905. doi: 10.3390/microorganisms9050905

Jarvis, K. G., Daquigan, N., White, J. R., Morin, P. M., Howard, L. M., Manetas, J. E., et al. (2018). Microbiomes associated with foods from plant and animal sources. Front. Microbiol. 9:2540. doi: 10.3389/fmicb.2018.02540

Kandel, C. E., Simor, A. E., and Redelmeier, D. A. (2014). Elevator buttons as unrecognized sources of bacterial colonization in hospitals. Open Med. 8, e81–e86

PubMed Abstract | Google Scholar

Kubo, M. T., Siguemoto, É. S., Funcia, E. S., Augusto, P. E., Curet, S., Boillereaux, L., et al. (2020). Non-thermal effects of microwave and ohmic processing on microbial and enzyme inactivation: a critical review. Curr. Opin. Food Sci. 35, 36–48. doi: 10.1016/j.cofs.2020.01.004

Kumar, K. V., Pal, A., Bai, P., Kour, A., E, S., P, R., et al. (2019). Co-aggregation of bacterial flora isolated from the human skin surface. Microb. Pathog. 135:103630. doi: 10.1016/j.micpath.2019.103630

Lacap, D. C., Warren-Rhodes, K. A., McKay, C. P., and Pointing, S. B. (2011). Cyanobacteria and chloroflexi-dominated hypolithic colonization of quartz at the hyper-arid core of the Atacama Desert, Chile. Extremophiles 15, 31–38. doi: 10.1007/s00792-010-0334-3

Lax, S., Hampton-Marcell, J. T., Gibbons, S. M., Colares, G. B., Smith, D., Eisen, J. A., et al. (2015). Forensic analysis of the microbiome of phones and shoes. Microbiome 3:21. doi: 10.1186/s40168-015-0082-9

Leung, P. H. M., Subramanya, R., Mou, Q., Lee, K. T., Islam, F., Gopalan, V., et al. (2019). Characterization of mucosa-associated microbiota in matched Cancer and non-neoplastic mucosa from patients with colorectal Cancer. Front. Microbiol. 10:1317. doi: 10.3389/fmicb.2019.01317

Liedert, C., Peltola, M., Bernhardt, J., Neubauer, P., and Salkinoja-Salonen, M. (2012). Physiology of resistant Deinococcus geothermalis bacterium aerobically cultivated in low-manganese medium. J. Bacteriol. 194, 1552–1561. doi: 10.1128/JB.06429-11

Madueño, L., Coppotelli, B. M., Festa, S., Alvarez, H. M., and Morelli, I. S. (2018). Insights into the mechanisms of desiccation resistance of the Patagonian PAH-degrading strain Sphingobium sp. 22B. J. Appl. Microbiol. 124, 1532–1543. doi: 10.1111/jam.13742

Maleki, F., Khosravi, A., Nasser, A., Taghinejad, H., and Azizian, M. (2016). Bacterial heat shock protein activity. J. Clin. Diagn. Res. 10:BE01–BE03. doi: 10.7860/JCDR/2016/14568.7444

Mallick, H., Rahnavard, A., McIver, L. J., Ma, S., Zhang, Y., Nguyen, L. H., et al. (2021). Multivariable association discovery in population-scale meta-omics studies. PLOS Computational Biology , 17:e1009442. doi: 10.1371/journal.pcbi.1009442

Malta, R. C. R., Ramos, G. L. De, and Nascimento, J. S. (2020). From food to hospital: we need to talk about Acinetobacter spp. Germs , 10, 210–217. doi: 10.18683/germs.2020.1207

Mattimore, V., and Battista, J. R. (1996). Radioresistance of Deinococcus radiodurans : functions necessary to survive ionizing radiation are also necessary to survive prolonged desiccation. J. Bacteriol. 178, 633–637. doi: 10.1128/jb.178.3.633-637.1996

McMurdie, P. J., and Holmes, S. (2013). Phyloseq: an R package for reproducible interactive analysis and graphics of microbiome census data. PLoS One 8:e61217. doi: 10.1371/journal.pone.0061217

Molano, L.-A. G., Vega-Abellaneda, S., and Manichanh, C. (2024). GSR-DB: a manually curated and optimized taxonomical database for 16S rRNA amplicon analysis. mSystems 9, e00950–e00923. doi: 10.1128/msystems.00950-23

Moskovicz, V., Ben-El, R., Horev, G., and Mizrahi, B. (2021). Skin microbiota dynamics following B. subtilis formulation challenge: an in vivo study in mice. BMC Microbiol. 21:231. doi: 10.1186/s12866-021-02295-y

Munteanu, A.-C., Uivarosi, V., and Andries, A. (2015). Recent progress in understanding the molecular mechanisms of radioresistance in Deinococcus bacteria. Extremophiles 19, 707–719. doi: 10.1007/s00792-015-0759-9

Nayak, T., Sengupta, I., and Dhal, P. K. (2021). A new era of radiation resistance bacteria in bioremediation and production of bioactive compounds with therapeutic potential and other aspects: an in-perspective review. J. Environ. Radioact. 237:106696. doi: 10.1016/j.jenvrad.2021.106696

Paczosa, M. K., and Mecsas, J. (2016). Klebsiella pneumoniae : going on the offense with a strong defense. Microbiol. Mol. Biol. Rev. 80, 629–661. doi: 10.1128/mmbr.00078-15

Pinna, A., Usai, D., Sechi, L. A., Zanetti, S., Jesudasan, N. C. A., Thomas, P. A., et al. (2009). An Outbreak of Post-Cataract Surgery Endophthalmitis Caused by Pseudomonas aeruginosa. Ophthalmology , 116, 2321–2326.e4. doi: 10.1016/j.ophtha.2009.06.004

Podschun, R., and Ullmann, U. (1998). Klebsiella spp. as nosocomial pathogens: epidemiology, taxonomy, typing methods, and pathogenicity factors. Clin. Microbiol. Rev. 11, 589–603. doi: 10.1128/CMR.11.4.589

Porcar, M., Louie, K. B., Kosina, S. M., Van Goethem, M. W., Bowen, B. P., Tanner, K., et al. (2018). Microbial ecology on solar panels in Berkeley, CA, United States. Front. Microbiol. 9:3043. doi: 10.3389/fmicb.2018.03043

Raghupathi, P. K., Zupančič, J., Brejnrod, A. D., Jacquiod, S., Houf, K., Burmølle, M., et al. (2018). Microbial diversity and putative opportunistic pathogens in dishwasher biofilm communities. Appl. Environ. Microbiol. 84, e02755–e02717. doi: 10.1128/AEM.02755-17

Rodrigues, C., Hauser, K., Cahill, N., Ligowska-Marzęta, M., Centorotola, G., Cornacchia, A., et al. (2022). High prevalence of Klebsiella pneumoniae in European food products: a multicentric study comparing culture and molecular detection methods. Microbiol. Spectr. 10:e0237621. doi: 10.1128/spectrum.02376-21

Roy, S., and Roy, M. (2019). Characterization of plant growth promoting feature of a neutromesophilic, facultatively chemolithoautotrophic, Sulphur oxidizing bacterium Delftia sp. strain SR4 isolated from coal mine spoil. Int. J. Phytoremediation 21, 531–540. doi: 10.1080/15226514.2018.1537238

Ryan, M. P., and Pembroke, J. T. (2018). Brevundimonas spp: emerging global opportunistic pathogens. Virulence 9, 480–493. doi: 10.1080/21505594.2017.1419116

Satari, L., Guillén, A., Vidal-Verdú, À., and Porcar, M. (2020). The wasted chewing gum bacteriome. Sci. Rep. 10:16846. doi: 10.1038/s41598-020-73913-4

Sghaier, H., Ghedira, K., Benkahla, A., and Barkallah, I. (2008). Basal DNA repair machinery is subject to positive selection in ionizing-radiation-resistant bacteria. BMC Genomics 9:297. doi: 10.1186/1471-2164-9-297

Shaker, R., Osaili, T., Al-Omary, W., Jaradat, Z., and Al-Zuby, M. (2007). Isolation of Enterobacter sakazakii and other Enterobacter sp. from food and food production environments. Food Control 18, 1241–1245. doi: 10.1016/j.foodcont.2006.07.020

Shaw, P., Kumar, N., Mumtaz, S., Lim, J. S., Jang, J. H., Kim, D., et al. (2021). Evaluation of non-thermal effect of microwave radiation and its mode of action in bacterial cell inactivation. Sci. Rep. 11:14003. doi: 10.1038/s41598-021-93274-w

Shen, Q., Ji, F., Wei, J., Fang, D., Zhang, Q., Jiang, L., et al. (2020). The influence mechanism of temperature on solid phase denitrification based on denitrification performance, carbon balance, and microbial analysis. Sci. Total Environ. 732:139333. doi: 10.1016/j.scitotenv.2020.139333

Shu, W.-S., and Huang, L.-N. (2022). Microbial diversity in extreme environments. Nat. Rev. Microbiol. 20, 219–235. doi: 10.1038/s41579-021-00648-y

Silby, M. W., Nicoll, J. S., and Levy, S. B. (2009). Requirement of polyphosphate by Pseudomonas fluorescens Pf0-1 for competitive fitness and heat tolerance in laboratory media and sterile soil. Appl. Environ. Microbiol. 75, 3872–3881. doi: 10.1128/AEM.00017-09

Singh, A., Pandey, A. K., and Dubey, S. K. (2023). Genome sequencing and in silico analysis of isoprene degrading monooxygenase enzymes of Sphingobium sp. BHU LFT2. J. Biomol. Struct. Dyn. 41, 3821–3834. doi: 10.1080/07391102.2022.2057360

Skowron, K., Bauza-Kaszewska, J., Kraszewska, Z., Wiktorczyk-Kapischke, N., Grudlewska-Buda, K., Kwiecińska-Piróg, J., et al. (2021). Human skin microbiome: impact of intrinsic and extrinsic factors on skin microbiota. Microorganisms 9:543. doi: 10.3390/microorganisms9030543

Speirs, J. P., Anderton, A., and Anderson, J. G. (1995). A study of the microbial content of the domestic kitchen. Int. J. Environ. Health Res. 5, 109–122. doi: 10.1080/09603129509356839

Tanner, K., Martí, J. M., Belliure, J., Fernández-Méndez, M., Molina-Menor, E., Peretó, J., et al. (2018). Polar solar panels: Arctic and Antarctic microbiomes display similar taxonomic profiles. Environ. Microbiol. Rep. 10, 75–79. doi: 10.1111/1758-2229.12608

Tanner, K., Molina-Menor, E., Latorre-Pérez, A., Vidal-Verdú, À., Vilanova, C., Peretó, J., et al. (2020). Extremophilic microbial communities on photovoltaic panel surfaces: a two-year study. Microb. Biotechnol. 13, 1819–1830. doi: 10.1111/1751-7915.13620

Thomas, P. (2012). Long-term survival of Bacillus spores in alcohol and identification of 90% ethanol as relatively more spori/bactericidal. Curr. Microbiol. 64, 130–139. doi: 10.1007/s00284-011-0040-0

Uribe-Lorío, L., Brenes-Guillén, L., Hernández-Ascencio, W., Mora-Amador, R., González, G., Ramírez-Umaña, C. J., et al. (2019). The influence of temperature and pH on bacterial community composition of microbial mats in hot springs from Costa Rica. Microbiologyopen 8:e893. doi: 10.1002/mbo3.893

Vilanova, C., Iglesias, A., and Porcar, M. (2015). The coffee-machine bacteriome: biodiversity and colonisation of the wasted coffee tray leach. Sci. Rep. 5:17163. doi: 10.1038/srep17163

Woo, I. S., Rhee, I. K., and Park, H. D. (2000). Differential damage in bacterial cells by microwave radiation on the basis of cell wall structure. Appl. Environ. Microbiol. 66, 2243–2247. doi: 10.1128/AEM.66.5.2243-2247.2000

Keywords: microwave, 16S rRNA gene sequencing, taxonomic classification, radiation, desiccation, selective pressure

Citation: Iglesias A, Martínez L, Torrent D and Porcar M (2024) The microwave bacteriome: biodiversity of domestic and laboratory microwave ovens. Front. Microbiol . 15:1395751. doi: 10.3389/fmicb.2024.1395751

Received: 04 March 2024; Accepted: 19 June 2024; Published: 08 August 2024.

Reviewed by:

Copyright © 2024 Iglesias, Martínez, Torrent and Porcar. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) . The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

*Correspondence: Manuel Porcar, [email protected]

† ORCID: Alba Iglesias, http://orcid.org/0000-0002-6582-9747 Daniel Torrent, http://orcid.org/0000-0002-3997-0974 Manuel Porcar, http://orcid.org/0000-0002-7916-9479

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Microwaved Water Kills Plants-Fiction!

Summary of eRumor: A viral email claims that an experiment at a science fair proved that water that has been heated with a microwave oven kills plants. The eRumor also alleged that eating microwaved foods leads to brain damage and other serious health conditions.  

The TruthorFiction.com Team contacted the England-based Association for Research Ethics, which sometimes uses the acronym “A.R.E.C.” that is found on the warning that was allegedly authored by William P. Kopp.

We are waiting for a response, and updates will be posted here.

Posted 05/01/14