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Tag: Microbiology

  • A surprisingly wide range of bacteria live inside microwaves

    A surprisingly wide range of bacteria live inside microwaves

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    Microwaves heat up food, but don’t necessarily kill bacteria

    Shutterstock/stockfoto

    Microwave ovens in homes, offices and laboratories are home to a surprising diversity of bacteria.

    Although microwaves are widely used to heat up food and sterilise samples, the radiation they emit is non-ionising, which means that it doesn’t damage biological molecules. They heat things up by making water molecules vibrate, but this only kills bacteria if they reach a high enough temperature.

    Nevertheless, repeated bouts of heating and drying mean that microwaves were thought to be a difficult environment for microorganisms to survive in.

    Alba Iglesias at the University of Valencia, Spain, and her colleagues took samples from 30 microwave ovens: 10 from single-household, domestic kitchens; 10 from shared kitchens such as corporate centres, scientific institutes and cafeterias; and 10 from molecular biology and microbiology laboratories.

    In total, the researchers found 747 different genera of bacteria within 25 bacterial phyla. Diversity was lowest in single-household microwaves, and highest in laboratory appliances.

    Many of the bacteria found in shared, domestic microwaves and the single-household microwaves overlapped, and were similar to the bacteria often found on human hands and in other parts of the kitchen. However, those in labs, where food was not cooked, were more distinct and were similar to the microbiome found in other extreme, dry, hot and irradiated environments, such as on solar panels.

    The researchers noted that some bacteria found in domestic microwaves, such as Klebsiella, Enterococcus and Aeromonas, may pose a risk to human health. However, they say the microbial population found in microwaves does not present a unique or increased risk compared with other common kitchen surfaces. The researchers didn’t respond to an interview request.

    Belinda Ferrari at the University of New South Wales, Australia, says she is not surprised at all that the researchers found bacteria living in microwaves. “They can survive in almost any extreme-exposure environment and they can adapt to everything,” she says.

    Ferrari recommends regularly cleaning microwaves with disinfectant products. “Some workplace microwaves are disgusting and no one cleans them,” she says.

    She would like to see more information in the study about when the microwaves were last cleaned. “If I was doing this experiment, I would also like to study the biome before and after cleaning,” she says.

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  • Your microwave oven has its own microbiome

    Your microwave oven has its own microbiome

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    A close-up of hands operating a microwave

    After reading this story, you might want to clean your microwave oven.Credit: Maksim Kostenko/Alamy

    ‘Extremophiles’ are organisms that can survive, and even thrive, in the harshest of environments, including inside scorching hydrothermal vents, sub-zero Antarctic ice and the crushing pressures of Earth’s crust. Now, they’ve been discovered in a more pedestrian setting: microwave ovens.

    Although previous studies found distinct communities of microbes in kitchen appliances such as dishwashers1 and coffee machines2, this is the first time that the microwave oven has been investigated for having its own microbiome. The research, published today in Frontiers in Microbiology3, adds to existing work challenging a common misconception: that microwave radiation heats up and completely kills bacteria that cause food-borne illness, such as Escherichia coli and Salmonella.

    “We’ve all been taught, from like the 1980s, that if you use a microwave oven, it heats everything up — it kills everything,” says Jason Tetro, a freelance microbiologist, known as ‘The Germ Guy’, in Edmonton, Canada. This study is “important”, he says, because it shines a spotlight on potential pathogens in these appliances, especially shared ones.

    All that’s zapped is not killed

    Alba Iglesias, a microbiologist at the University of Valencia in Spain, and her colleagues swabbed 30 microwave ovens — including some in households; some shared in large spaces, such as offices; and some used in laboratories to heat specimens and chemical solutions. The team then cultured its samples in Petri dishes and determined the genera of the microbes that grew. They also sequenced the DNA in the material swabbed from the microwave ovens to get a sense of the bacterial diversity inside the appliances.

    These microbial communities have learned to live at Earth’s most extreme reaches

    A total of 101 bacterial strains grew in the cultures. The dominant ones belonged to the Bacillus, Micrococcus and Staphylococcus genera, which commonly live on human skin and surfaces that people frequently touch. Human-skin bacteria were present in all three types of microwave oven, but were more abundant in the household and shared-use appliances. A few bacteria types associated with food-borne illnesses, including Klebsiella and Brevundimonas, also grew in some of the cultures from household microwaves.

    Laboratory microwave ovens contained the greatest genetic diversity of bacteria. The researchers found both kitchen-counter bacteria and extremophiles that can withstand the radiation, high temperatures and extreme dryness in these appliances.

    “You don’t need to go to very exotic — geographically speaking — places to find diversity of microorganisms,” says co-author Manuel Porcar, a microbiologist also at the University of Valencia in Spain.

    The team suggests that the extremophile strains they found in the microwave ovens might have been ‘selected’ evolutionarily by surviving repeated rounds of radiation, and could have biotechnological applications, such as in the bioremediation of toxic waste. Porcar says that the next step is to investigate how microwave usage might affect these bacteria over time.

    But for the general public, the implications of the study are simpler. “A microwave is not a pure, pristine place,” Porcar says. It’s also not a pathogenic reservoir to be feared, he says. But he does recommend cleaning your kitchen microwave often — just as often as you would scrub your kitchen surfaces to eliminate potential bacteria.

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  • A joint bacterial effort to produce vitamin B<sub>12</sub>

    A joint bacterial effort to produce vitamin B<sub>12</sub>

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    Nature, Published online: 31 July 2024; doi:10.1038/d41586-024-02474-7

    Vitamin B12 consists of two molecular components and has been thought to be synthesized only in full by certain bacteria. It emerges that two bacterial strains that each exclusively produce one building block can complement each other to enable joint synthesis of the vitamin.

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  • The vital viruses that shape your microbiome and your health

    The vital viruses that shape your microbiome and your health

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    New Scientist. Science news and long reads from expert journalists, covering developments in science, technology, health and the environment on the website and the magazine.

    Withdrawn and anxious, the mice in John Cryan’s lab were behaving like you or I might if we had experienced workplace bullying and thought we might encounter the bully again.

    The good news, believe it or not, was that some of these rodents were also being fed a slurry of microbes derived from their own faeces. Unpalatable as this sounds, it had a surprisingly positive effect on their behaviour. “It was phenomenal,” says Cryan, a neurobiologist at University College Cork in Ireland. “We found that these stress-induced changes in behaviour normalised – they started to behave just like normal animals.”

    Even more surprising, this mental transformation wasn’t brought about by changing the bacteria in their guts, but by tinkering with another crucial facet of the microbiome whose importance is only now being recognised: viruses.

    It turns out that we are riddled with these. Not the ones that make us unwell, but trillions of stowaways that play a crucial role in cultivating a beneficial microbiome and making us healthier in turn. Recent research shows that the influence of this “virome” can be found across the body, from the blood to the brain. The hope is that by tweaking it, we could find new ways of treating various ailments, from inflammatory bowel disease and obesity to anxiety.

    Microbiome diversity

    The past decade has seen a surge of interest in the microbiome – all the really tiny things that live on and in us – but this has largely focused on bacteria. The assumption until recently was that…

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  • Gut microbiome discovery provides roadmap for life-saving cancer therapies

    Gut microbiome discovery provides roadmap for life-saving cancer therapies

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    Computer illustration of veillonella bacteria shown in red and orange colours

    A bacterial grouping that includes the genus Veillonella (artificially coloured) has been linked to a lower rate of response to cancer immunotherapy. Credit: Kateryna Kon/Science Photo Library

    Despite their small size, gut bacteria wield large influence over the effectiveness of certain cancer drugs. Researchers have now found that the ratio of specific microbial communities in the gut can help to predict who will respond to next-generation drugs for treating some kinds of cancer1.

    The findings will also help to identify healthy volunteers who could donate faecal bacteria to transfer into the intestines of people who do not respond to these drugs, a procedure known as faecal microbiome transplantation, study co-author Laurence Zitvogel, an immunologist and oncologist at the Gustave Roussy Cancer Campus in Villejuif, France, wrote in an e-mail to Nature.

    The work “is a breakthrough from a diagnostic point of view”, says Fabio Grassi, an immunologist at the Institute for Research in Biomedicine in Bellinzona, Switzerland. The findings, he says, also highlight how the delicate balance of gut microbial species can affect the success of high-stakes therapies, such as immune checkpoint inhibitors. This treatment helps the immune system to recognize and attack cancer cells and is the focus of the new research. The findings were published today in Cell.

    Search for helper bacteria

    Over the past decade, Zitvogel and others have investigated how gut microbes interact with these cancer treatments in ways that activate the immune system. “Everyone was looking for that single bug that [could] improve response to immunotherapy across cancer types — and it was elusive,” says Jennifer Wargo, a physician-scientist at the University of Texas MD Anderson Cancer Center in Houston. In 2018, Wargo published a study2 — alongside similar ones by Zitvogel3 and a third team4 — that linked specific gut bacteria to positive clinical outcomes following immunotherapy treatment in mice and people with cancer. But there was little agreement on which microbial species were associated with treatment response.

    Wargo says that Zitvogel’s latest research helps to answer why the search for a single gut microbe that could boost responses to cancer immunotherapy was so challenging. Instead of focusing on individual microbial species, the work shows that the overall make-up of microbial communities in the gut influences a person’s response. “It’s all about the community structure,” Wargo says.

    Why are so many young people getting cancer? What the data say

    Zitvogel and her colleagues analysed faecal samples from 245 people with lung cancer and identified two groups of microbial species: group one contained 37 microbes, such as Veillonella species, that are linked to resistance to immune checkpoint inhibitors; group two included 45 bacterial species associated with positive responses. People with lung cancer with response-associated bacteria lived longer than did those with resistance-associated bacteria.

    Next, the researchers developed a person-specific score based on the ratio between group one and group two. The score also included quantification of Akkermansia muciniphila, a microbe that has gained attention owing to its potential role in influencing immune responses.

    When tested on hundreds of people with various types of cancer, including kidney cancer, the score could predict in most cases who was likely to respond to treatment with immune checkpoint inhibitors. The score will soon be transformed into a diagnostic assay, Zitvogel wrote.

    Possible predictive tool

    The tool could help to identify people with cancer who might need microbiome-targeting therapies to boost their response to immunotherapy, but it requires further validation before it can be used in the clinic, says Francesca Gazzaniga, a biologist at Massachusetts General Hospital in Boston.

    She also notes that the study focused on participants in Canada and France, so the score might not be as predictive in populations living in different areas and eating different diets, Gazzaniga says. “This is a good start, and if we understand more about the underlying mechanisms — why these sets of bacteria are important — we might be able to get better targeted therapies.”

    Research on the role of microbiota in the response to immunotherapy began years ago, yet there have been no tangible benefits for patients so far, says Maria Rescigno, an immunologist at Humanitas University in Milan, Italy. All the same, Rescigno anticipates that doctors will integrate the tool developed by Zitvogel and her team into practice. “If clinicians adopt this, it could lead to a significant change for the patients.”

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  • Could we merge biologically with the fungal network and live forever?

    Could we merge biologically with the fungal network and live forever?

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    In this week’s Future Chronicles column, which explores an imagined history of future inventions, we visit a cult in 2080s Japan that engineered a way of becoming chimeric with fungal biology. Rowan Hooper reveals their history

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  • Microbes ‘sieve’ ions on their surface to start the nitrogen cycle

    Microbes ‘sieve’ ions on their surface to start the nitrogen cycle

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    Nature, Published online: 29 May 2024; doi:10.1038/d41586-024-01351-7

    Uptake of ammonium ions by marine microorganisms called archaea is a key first step in the conversion of ammonium to nitrogen found in ecosystems. Structural evidence reveals how archaea capture ammonium in an efficient way.

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  • Nitrogen-hungry bacteria added to farm soil curb greenhouse-gas emissions

    Nitrogen-hungry bacteria added to farm soil curb greenhouse-gas emissions

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    Nature, Published online: 29 May 2024; doi:10.1038/d41586-024-01363-3

    Innovative solutions are needed to decrease greenhouse-gas emissions. Field trials show that supplementing farm soil with a bacterium that consumes the greenhouse gas nitrous oxide can substantially lower harmful emissions.

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  • ‘Smart’ antibiotic can kill deadly bacteria while sparing the microbiome

    ‘Smart’ antibiotic can kill deadly bacteria while sparing the microbiome

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    False-colour scanning electron micrograph of a colony of the bacteria Klebsiella pneumonia.

    Gram-negative bacteria such as Klebsiella pneumoniae (artificially coloured) are often resistant to multiple antibiotics, but they succumb to a new compound called lolamicin.Credit: Dr Tony Brain/Science Photo Library

    They are the stuff of medical nightmares. Pathogens classified as Gram-negative bacteria are often hardy, virulent and quick to evolve resistance to antibiotics. Only a few drugs can knock them out, and these also destroy beneficial gut bacteria.

    Now scientists have developed an antibiotic that kills pathogenic Gram-negative bacteria — even those resistant to many other drugs — without impairing the gut microbiome. So far, it has been studied only in mice, but if the compound works in humans, “it could help us dramatically”, says Sebastian Hiller, a structural biologist at the University of Basel in Switzerland who was not involved in the research. However, there is a caveat, he says: the compound’s usefulness “depends on whether bacteria will develop resistance to it in the long run”.

    The study appears today in Nature.

    Small but deadly

    Gram-negative bacteria include public-health villains such as Escherichia coli and Klebsiella pneumoniae. They cause diseases ranging from salmonella to cholera, and can trigger sepsis, a potentially lethal immune-system response to infection.

    The bacteria have “multiple barriers that prevent antibiotic penetration”, says molecular biologist Zemer Gitai at Princeton University in New Jersey, who was not involved in the research. As a result, there are almost no antibiotics that specifically target Gram-negative bacteria. The few drugs that do also wreak havoc with the gut microbiome, allowing potentially deadly pathogens such as Clostridioides difficile to take over.

    UTIs make life miserable — scientists are finding new ways to tackle them

    To find a way around the bacteria’s defences, the study’s authors started with compounds that don’t kill the bacteria but are known to inhibit the ‘Lol system’, a group of proteins that is exclusive to Gram-negative bacteria. Tinkering with those compounds produced one that the researchers called lolamicin, which “selectively kills pathogenic bacteria over non-pathogenic bacteria based on differences in Lol proteins between these bacteria”, says study co-author Paul Hergenrother, a chemist at the University of Illinois at Urbana-Champaign.

    Lolamicin had anti-microbial effects against more than 130 multidrug-resistant strains of bacteria growing in laboratory dishes. Mice that developed blood stream infections after exposure to antibiotic-resistant bacteria all survived after being given lolamicin, whereas 87% of those that didn’t receive the compound died within three days.

    The team also found that common antibiotics such as amoxicillin severely disrupted the animals’ gut microbiome, which led to infections with C. difficile. By contrast, lolamicin treatment did not cause observable changes in the gut microbiome and spared mice from C. difficile infection.

    ‘A long road’

    Gitai says that the study “proves the viability” of targeting the Lol system, but adds, “There is a long road from showing efficacy in mice to developing a drug for human use.”

    Hiller also sounds a cautious note. The time from an antibiotic’s discovery to its approval for clinical use can be more than two decades, “and there is not much money to be made with a novel antibiotic”, he says. “Around ten to twenty new Gram-negative antibiotics have been discovered in the last ten years”, he adds, but none has gained approval from the US Food and Drug Administration.

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  • Bizarre bacteria defy textbooks by writing new genes

    Bizarre bacteria defy textbooks by writing new genes

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    A computer rendered illstration of an RNA molecule.

    A bacterial enzyme turns biology on its head by reading RNA (artist’s illustration) into DNA that forms new genes.Credit: Artur Plawgo/Science Photo Library

    Genetic information usually travels down a one-way street: genes written in DNA serve as the template for making RNA molecules, which are then translated into proteins. That tidy textbook story got a bit complicated in 1970 when scientists discovered that some viruses have enzymes called reverse transcriptases, which scribe RNA into DNA — the reverse of the usual traffic flow.

    Now, scientists have discovered an even weirder twist1. A bacterial version of reverse transcriptase reads RNA as a template to make completely new genes written in DNA. These genes are then transcribed back into RNA, which is translated into protective proteins when a bacterium is infected by a virus. By contrast, viral reverse transcriptases don’t make new genes; they merely transfer information from RNA to DNA.

    “This is crazy molecular biology,” says Aude Bernheim, a bioinformatician at the Pasteur Institute in Paris, who was not involved in the research. “I would have never guessed this type of mechanism existed.”

    One-up on CRISPR

    Bacteria fend off viruses and other invaders by deploying myriad defences, such as the juggernaut gene-editing system CRISPR. One of the more mysterious defence systems contains the DNA gene for a reverse transcriptase and a short stretch of mysterious RNA without any clear function: the sequence didn’t seem to encode any protein.

    To work out how this system works, a team co-led by molecular biologist Stephen Tang and biochemist Samuel Sternberg, both at Columbia University in New York City, searched for the DNA molecules made by a reverse transcriptase from bacteria called Klebsiella pneumoniae. It found very long DNA sequences that consisted of numerous identical repeating segments. Each segment matched a chunk of the mysterious RNA.

    Loop-the-loop

    To explain this, the authors note that long RNA strands can form hairpin-like shapes, bringing two distant portions close to each other. The researchers found that the K. pneumoniae reverse transcriptase was doing repeated ‘laps’ around the RNA sequence, which was looped over itself like a shoelace, writing the same RNA molecule into DNA many times over. This created a repetitive DNA sequence.

    How scientists are hacking the genetic code to give proteins new powers

    The repeated segments created a protein-coding sequence called an open reading frame. The researchers named this sequence neo, for ‘never-ending open reading frame’, because it lacks a sequence that signals the end of a protein and, therefore, theoretically has no limit. They then found that viral infection triggers the production of the Neo protein, which causes cells to stop dividing. The findings, which have not yet been peer reviewed, were posted to the bioRxiv preprint server on 8 May.

    How Neo halts growth of infected cells isn’t yet clear, the researchers say. A predicted 3D structure of a portion of Neo — its length probably varies depending on how much of its RNA gets translated — suggests that it forms a series of helices. Experiments showed that breaking up these shapes stymied Neo’s toxic effects. Exactly how viral infection kicks off the creation of the Neo protein is also a mystery, says Bernheim. “This I am burning to know.”

    Wonderful life

    The discovery that reverse transcriptase — which has previously been known only for copying genetic material — can create completely new genes has left other researchers gobsmacked. “This looks like biology from alien organisms,” Israel Fernandez, a computational chemist at Complutense University of Madrid, wrote on X.

    “Their findings were astonishing,” says Nicolás Toro García, a molecular biologist at Zaidín Experimental Research Station in Grenada, Spain, and should help researchers to develop biotechnology applications for the system.

    The discovery has even left Sternberg in awe: “It should change the way we look at the genome.”

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