Using next-generation sequencing and cultivation techniques, the study shows that the bacterial population in microwave ovens is dominated by a composition similar to human skin and does not pose health problems.

Microwave ovens, essential in modern kitchens, still represent unexplored territory from the point of view of microbial studies. To understand their potential as a reservoir for bacterial colonization and the microbial composition of their interior, research staff from DARWIN Bioprospecting Excellence and the Institute of Integrative Systems Biology (I2SysBio) have collaborated on a study published in the open-access journal Frontiers.

Using next-generation sequencing and culturing techniques, the study shows that the bacterial population in microwave ovens is dominated by Proteobacteria, Firmicutes, Actinobacteria, and Bacteroidetes, similar to the bacterial composition of human skin. Comparison with other environments reveals that the bacterial composition of household microwaves is similar to that of kitchen surfaces, while laboratory microwaves have a higher abundance of taxa known for their ability to withstand microwave radiation, high temperatures, and desiccation.

“The motivation for the study is basic science, first of all, to see what is there and in a habitat that has not been well described from a microbiological point of view before and to answer a fundamental biological question about the selective pressure responsible for a particular microbial community. In a microwave, there is a very clear selective pressure in the form of temperature, high irradiation, and desiccation, among other factors,” explains Manel Porcar, CEO of DARWIN Bioprospecting Excellence and researcher at I2SysBio, whose research group has analyzed similar exotic environments such as Nespresso coffee machines, solar panels or chewing gum stuck to the ground. “As microbial ecologists, we are dedicated to studying the microbial communities that exist in numerous habitats on our planet, and this includes not only natural ones but also artificial habitats,” he adds.

Among the main findings, the study shows that “not all microwaves are the same. Basically, there are two large groups of microwaves: those for domestic use and those for laboratory use. Unlike domestic microwaves, we have observed that those used in laboratories have much less organic matter, so we have found taxa that are typically resistant to radiation, which makes these microwaves suitable for use in a high-radiation environment such as a desert or surface-facing full sunlight,” describes Daniel Torrent, bioinformatician at DARWIN Bioprospecting Excellence.