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Biologists find a variety of bacterial communities in microwave ovens

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Microwave ovens have become an essential part of the modern kitchen, yet their potential as a reservoir for bacterial colonization and the microbial composition within them remain largely unknown. In a new study, microbiologists from the University of Valencia and Darwin Bioprospecting Excellence SL investigated the bacterial communities within microwave ovens and compared the microbial composition of domestic microwave ovens, microwaves used in large shared spaces, and laboratory microwaves. The bacterial populations in microwave ovens were 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 microwave ovens was similar to that of kitchen surfaces, while laboratory microwave ovens contained a higher proportion of species known to tolerate microwave radiation, high temperatures, and dryness.

Iglesias othersMicrowaves were shown to harbor specialized communities of locally adapted microbial genera similar to those reported on kitchen surfaces and solar panels, environments with extremely high radiation exposure.

Microorganisms thriving in ecosystems characterized by extreme environmental conditions have been well studied to elucidate the evolutionary mechanisms that favor their adaptation.

Natural extreme environments are an excellent source of new microbial species as well as new secondary metabolites for biotechnological applications, but we don’t have to go very far to find them.

Microwave irradiation has been used for decades to reduce the presence of microorganisms in foods and to extend the shelf life of foods.

The application of electromagnetic waves in the range of 300 MHz to 300 GHz to a dielectric medium such as food (also known as microwave heating) produces heat that reaches a lethal temperature that inactivates most microorganisms. E. coli, Enterococcus faecalis, Clostridium perfringens, Staphylococcus aureus, Salmonella and Listeria Genus

Recent studies have shown that cellular inactivation is associated with inactivation of genes controlling oxidation, DNA damage, increased permeability, and reduced cell membrane integrity.

Despite this extensive characterization of the biological effects of microwave radiation on foodborne pathogens, there have been no reports of microwaves being a microbial niche, an environment in which a specifically adapted microbiota can form through specific selective pressures (in this case heat shock, microwave radiation, and desiccation).

“Our results reveal that domestic microwaves harbor a more 'humanised' microbiome, similar to kitchen surfaces, while laboratory microwaves harbour bacteria that are more resistant to radiation,” said Dr Daniel Trent, Darwin Bioprospecting Excellence SL researcher.

For the study, Dr Trent and his colleagues sampled microorganisms from inside 30 microwaves: 10 from household kitchens, 10 from shared household spaces such as corporate centers, science labs and cafeterias, and 10 from molecular biology and microbiology laboratories.

The aim of this sampling plan was to determine whether these microbial populations were influenced by interactions with food and by user habits.

They used two complementary methods to explore microbial diversity: next-generation sequencing and culturing 101 strains in five different media.

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

The researchers found that the composition of the general microbial community partially overlapped between shared and domestic microwave ovens, but was quite different in laboratory microwave ovens.

Diversity was lowest in home microwaves and highest in laboratory microwaves.

Members of the genus Acinetobacter, Bhargavaea, Brevibacterium, Brevundimonas, Dermatococcus, Klebsiella, Pantoea, Pseudoxanthomonas and Rhizobium It has only been found in domestic microwave ovens.

Arthrobacter, Enterobacter, Yanibacter, Methylobacterium, Neobacillus, Nocardioides, Novosphingobium, Paenibacillus, Peribacillus, Planococcus, Russia, Sporosarcinaand Teribacillus This was only seen in items shared within the household.

Nonomura The bacteria was isolated only from laboratory microwaves. Delftia, Micrococcus, Deinococcus Unidentified genera of the phylum Cyanobacteria were also common and were found at a significantly higher frequency than in Japan.

The researchers also compared the observed diversity with the diversity of specialized habitats reported in the literature.

As expected, the microbiome inside the microwave was similar to that present on typical kitchen surfaces.

“Some genera found in domestic microwave ovens include Klebsiella, Enterococcus and Aeromonaswhich could pose a health risk to humans,” Dr Trent said.

“However, it is important to note that the microorganisms living in microwave ovens do not pose any unique or increased risk compared to other common kitchen surfaces.”

But it also had similarities to the microbiome in industrial environments, namely on solar panels.

The scientists proposed that the constant heat shock, electromagnetic radiation and desiccation in this highly radioactive environment repeatedly selected for more resistant microorganisms, just as occurs in microwave ovens.

“We encourage both the public and laboratory personnel to regularly disinfect their microwave ovens with a diluted bleach solution or a commercially available disinfectant spray,” Dr. Trent said.

“In addition, it's important to wipe down interior surfaces with a damp cloth after each use to remove any residue and wipe up any spills immediately to prevent bacterial growth.”

of result Published in the journal The cutting edge of microbiology.

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Alba Iglesias others2024. The microwave bacteriome: biodiversity in domestic and laboratory microwave ovens. Front. Microbiol 15;doi: 10.3389/fmicb.2024.1395751

Source: www.sci.news

Microwave ovens are home to a surprising array of bacteria

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Microwaves heat food but don't necessarily kill bacteria

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Microwaves in homes, offices, and laboratories harbor a surprising variety of bacteria.

Microwaves are widely used to heat food and sterilize samples, but the radiation they emit is non-ionizing and does not damage biological molecules. Microwaves heat objects by vibrating water molecules, but bacteria are only killed if a high enough temperature is reached.

However, repeated heating and drying processes meant that microwaves were considered to be a difficult environment for microorganisms to survive.

Manuel Polker Researchers from the University of Valencia in Spain sampled 30 microwaves: 10 from private kitchens, 10 from shared kitchens such as corporate centers, scientific laboratories and cafeterias, and 10 from molecular biology and microbiology laboratories.

In total, the researchers found 747 different genera of bacteria within 25 bacterial phyla, with diversity lowest in domestic microwave ovens and highest in laboratory devices.

Many of the bacteria found in shared and single-family microwaves overlapped and were similar to bacteria commonly found on people's hands and elsewhere in the kitchen, suggesting that microbes don't need special adaptations to survive in microwaves, perhaps because food particles protect them from radiation, Polker said.

However, the microbiome found in the lab, where food was not cooked, was more distinctive and resembled those found in extremely dry, hot and irradiated environments, such as solar panels.

The researchers found that some of the bacteria found in household microwave ovens include: Klebsiella, Enterococcus and Aeromonaswhich may pose a risk to human health, but the microbial populations found on microwaves do not pose any unique or elevated risk compared to other common kitchen surfaces, the researchers said.

“What's clear is that the microwave cannot be trusted to be a cleaner environment in terms of microbes than the rest of the kitchen, and it should be cleaned just like the rest of the kitchen,” Polker says.

Belinda Ferrari A researcher from the University of New South Wales in Australia says she's not at all surprised that researchers found bacteria that can live in microwaves. “Bacteria can survive almost any extreme exposure and can adapt to anything,” she says.

Ferrari recommends regularly cleaning your microwave with a disinfectant: “Some microwaves in workplaces are filthy and no one cleans them,” she says.

She would like to see more detailed information about when microwaves were last cleaned in her research: “If we were to do this experiment, we would also like to study the biome before and after cleaning,” she says.

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Source: www.newscientist.com

Resilient bacteria discovered thriving in microwave ovens

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Microwaves heat food but don't necessarily kill bacteria

Shutterstock/Stock Photo

Microwaves in homes, offices, and laboratories harbor a surprising variety of bacteria.

Microwaves are widely used to heat food and sterilize samples, but the radiation they emit is non-ionizing and does not damage biological molecules. Microwaves heat objects by vibrating water molecules, but bacteria are only killed if a high enough temperature is reached.

However, repeated heating and drying processes meant that microwaves were considered to be a difficult environment for microorganisms to survive.

Alba Iglesias Researchers from the University of Valencia in Spain sampled 30 microwaves: 10 from private kitchens, 10 from shared kitchens such as corporate centers, scientific laboratories and cafeterias, and 10 from molecular biology and microbiology laboratories.

In total, the researchers found 747 different genera of bacteria within 25 bacterial phyla, with diversity lowest in domestic microwave ovens and highest in laboratory devices.

Many of the bacteria found in shared and single-family home microwaves overlapped and were similar to bacteria commonly found on people's hands and elsewhere in the kitchen, but the bacteria found in the lab, where no food is cooked, were more unique, resembling the microbiomes found in extremely dry, hot and irradiated environments, such as solar panels.

The researchers found that some of the bacteria found in household microwave ovens include: Klebsiella, Enterococcus and Aeromonaswhich could pose a risk to human health. But the microbial populations found on microwaves do not pose any unique or increased risk compared with other common kitchen surfaces, the researchers said. The researchers did not respond to requests for an interview.

Belinda Ferrari A researcher from the University of New South Wales in Australia says she's not at all surprised that researchers found bacteria that can live in microwaves. “Bacteria can survive almost any extreme exposure and can adapt to anything,” she says.

Ferrari recommends regularly cleaning your microwave with a disinfectant: “Some microwaves in workplaces are filthy and no one cleans them,” she says.

She would like to see more detailed information about when microwaves were last cleaned in her research: “If we were to do this experiment, we would also like to study the biome before and after cleaning,” she says.

topic:

Source: www.newscientist.com