Your Microwave Is Harboring Radiation-Resistant Microbes

Extreme environments – such as the International Space Station – are an exceptional source of novel microbial species and metabolites. Through evolution, these microbes have developed novel characteristics that hold potential in biotechnology applications.  

A new study published in Frontiers in Microbiology has found that highly-adapted microbes exist much closer to home – they’re in your kitchen. Specifically, they’re in your microwave.

These findings not only have implications for managing hygiene but also provide new information on the biotechnological potential of the microwave microbiome.

Microbes conquer microwave radiation

Inspired by the idea that common appliances, like microwaves, could host unique microbial ecosystems, the researchers from the University of Valencia and start-up Darwin Bioprospecting Excellence SL sampled the bacterial composition inside 30 microwaves from different environments (10 from domestic use, 10 from domestic shared use and 10 from laboratory use).

“Despite their [microwaves] frequent use, the bacterial communities within them had not been thoroughly studied. We wanted to understand how factors like microwave radiation and usage patterns shape these microbiomes and to explore potential biotechnological applications of these microbes,” Daniel Torrent, a researcher at Darwin Bioprospecting Excellence SL and one of the study's authors told Technology Networks.

Using next-generation sequencing the researchers identified that members of the phyla Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes, dominated the bacterial communities of the microwave, which also corresponds to the predominant phyla in the human skin microbiome.

In domestic microwaves, genera such as Shewanella, Enterobacter, Aeromonas, Lactococcus or Klebsiella were more abundant. These microbes are frequently detected in food-related habitats such as typical kitchen surfaces.

When asked if the microbes identified in domestic microwaves could be harmful to humans, Torrent explained, “Some bacteria belonging to genera that we have found in domestic microwaves, such as Klebsiella or Enterococcus, can potentially pose health risks. However, these genera are commonly found in food matrices and food-related habitats, typically associated with degradation or spoilage processes. Therefore, these risks cannot be considered greater than those associated with other kitchen surfaces.”

“To prevent these bacteria from contaminating food, it is important to keep the microwave clean,” continued Torrent. “This includes wiping down the interior after each use, cleaning up spills immediately and thoroughly sanitizing the microwave weekly with a household cleaner or diluted bleach solution. In addition, covering food while it is being heated can help reduce the spread of bacteria.”

Inside laboratory microwaves, the picture was quite different. Some of the genera that were significantly more abundant here included species known for their resistance to high doses of radiation, such as Deinococcus, Hymenobacter, Kineococcus, Sphingomonas and Cellulomonas.

When the researchers compared the bacterial communities of lab microwaves to those of other highly irradiated environments, the samples shared similarities to the microbiome of solar panel samples.

“Microwaves are environments where selection pressures are applied to the microorganisms that can inhabit them, such as high levels of radiation, high temperatures or desiccation,” explained Torrent. The authors propose that these selection pressures have led to highly resistant microbes, in the same manner as in solar panels and other extreme environments.

Repurposing microwave microbes

Further work is needed to study the microbial adaptations of strains isolated from microwaves, but the researchers hope that these microbes may be put to good use in industrial processes that require especially hardy bacteria.

“The tolerance to extreme conditions like high radiation of these bacteria could inspire several biotechnological applications,” said Torrent. “One of these may be bioremediation as a candidate for remediation by detoxifying, for example, radionuclides on site (in situ bioremediation) or in contaminated materials (ex situ bioremediation).”

Torrent concluded, “They [microbes] can also be used in industrial processes such as the production of biofuels or other chemicals, to enhance pretreatment processes or as biocatalysts in chemical reactions that require extreme conditions. In addition, some extremophilic bacteria have shown promising anti-pathogenic and anti-inflammatory activities. Of course, all of this requires a great deal of research, but having bacteria with these properties at hand could greatly facilitate these studies.”

Daniel Torrent was speaking to Blake Forman, Senior Science Writer for Technology Networks.

About the interviewee:

Daniel Torrent is a researcher at the start-up Darwin Bioprospecting Excellence SL in Paterna, Spain. Torrent earned his degree in biotechnology from the Valencia Polytechnic University where he also completed a master's degree in plant genetics.

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