Your microwave harbors radiation-resistant bacteria similar to solar panels

Humans don’t see microbes, but they are literally everywhere. You might think your microwave is a sterile environment. But think again. A new study has revealed a surprising truth: microbes thrive inside microwaves.

Researchers from Spain examined microwaves placed in homes, offices, and even laboratories. What they found was a hidden world of bacteria, with each setting harboring its own unique microbial community.

These microbes have adapted to survive the harsh conditions of a microwave such as significant temperature swings, radiation, and dryness.

“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.

Bacteria sampling in various microwaves

Microbes have adapted to thrive in a range of human-made environments, from marine oil spills to the International Space Station. In this study, the team was particularly interested in the presence of bacteria in the hot microwave setting.

The researchers gathered microbiological samples from 30 microwaves: 10 from private homes, 10 from shared communal spaces (like offices and cafeterias), and 10 from research laboratories.

To catalog the diversity of microbes, the researchers employed two methods: advanced genetic sequencing and traditional culturing of 101 strains across five different nutrient conditions.

Interestingly, scientists discovered a wide range of bacteria in the microwaves, although some were more prevalent than others.

Torrent and colleagues identified a total of 747 different groups (genera) of bacteria in their samples. The most prevalent bacteria groups were Firmicutes, Actinobacteria, and Proteobacteria. Proteobacteria were more abundant than the other two.

“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,” the press release explained.

Hardy bacteria may be used in biotechnology applications

The microwave environment supported a microbial population identical to that seen on ordinary kitchen surfaces — based on literature data.

“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 in the press release.

Surprisingly, the microbial community in microwaves also shared similarities with another unexpected environment: solar panels. The researchers hypothesized that the extreme conditions in these environments have led to the evolution of highly resilient microbes.

While some of these bacteria might pose a risk to human health, the researchers emphasize that the overall risk is similar to other kitchen surfaces.

In terms of hygiene, Torrent recommended: “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.”

However, this discovery opens up new possibilities. These hardy bacteria, which have evolved to tolerate such harsh environments, might be a goldmine for biotechnology. The researchers propose these resilient bacteria could be used in industrial processes that require bacteria capable of surviving harsh environments.

The study has been published in the journal Frontiers in Microbiology.