Just how clean is your microwave? Researchers from Spain have swabbed the insides of 30 different microwaves from household kitchens, offices, cafeterias and even microbiology labs to uncover the diversity of bacteria living in our microwaves. The microbes found in household microwaves resembled those found on typical kitchen surfaces, and while some of the species may pose a risk to human health, the researchers say it is probably no greater risk than other common kitchen surfaces. Interestingly, the microbes found in microwaves were also similar to those found on solar panels, and the authors say this could be because the heat and solar radiation on solar panels may have favoured highly resistant microbes, in the same manner as in microwaves. The researchers recommend regularly disinfecting microwaves with a diluted bleach solution or a commercially available disinfectant spray.
Journal/conference: Frontiers in Microbiology
Link to research (DOI): 10.3389/fmicb.2024.1395751
Organisation/s: Darwin Bioprospecting Excellence SL, Institute for Integrative Systems Biology (I²SysBio), Spain
Funder: 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.
Media release
From: Frontiers
Title: Microbes conquer the next extreme environment: your microwaveSubtitle: Radiation-resistant microbiome inside microwaves resembles that on solar panelsSummary: Researchers have measured the diversity of microbes inside microwaves for the first time. They showed that microwaves harbor a specialized community of locally adapted microbial genera, which resembles that reported on kitchen surfaces and in another extreme, highly irradiated habitat: on solar panels. This finding has potential biotechnological applications, in processes that require microbes resistant to thermal shock, radiation, and desiccation.Main text: 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 in a study in Frontiers in Microbiology by researchers from Spain. 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 cafeteria, 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.They used two complementary methods to inventorize the microbial diversity: next generation sequencing and cultivation of 101 strains on five different media.A biodiverse microhabitat right at homeIn 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 evolutionHowever, 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.###