Tag Archives: microbiome

Gut bacteriophages associated with improved cognitive function and memory in both animals and humans

A growing body of evidence has implicated gut bacteria in regulating neurological processes such as neurodegeneration and cognition. Now, a study from Spanish researchers shows that viruses present in the gut microbiota can also improve mental functions in flies, mice, and humans.

Credit: CDC.

They easily assimilate into their human hosts — 8% of our DNA consists of ancient viruses, with another 40% of our DNA containing genetic code thought to be viral in origin. As it stands, the gut virome (the combined genome of all viruses housed within the intestines) is a crucial but commonly overlooked component of the gut microbiome.

But we’re not entirely sure what it does.

This viral community is comprised chiefly of bacteriophages, viruses that infect bacteria and can transfer genetic code to their bacterial hosts. Remarkably, the integration of bacteriophages or phages into their hosts is so stable that over 80% of all bacterial genomes on earth now contain prophages, permanent phage DNA as part of their own — including the bacteria inside us humans. Now, researchers are inching closer to understanding the effects of this phenomenon.

Gut and brain

In their whitepaper published in the journal Cell Host and Microbe, a multi-institutional team of scientists describes the impact of phages on executive function, a set of cognitive processes and skills that help an individual plan, monitor, and successfully execute their goals. These fundamental skills include adaptable thinking, planning, self-monitoring, self-control, working memory, time management, and organization, the regulation of which is thought, in part, to be controlled by the gut microbiota.

The study focuses on the Caudovirales and Microviridae family of bacteriophages that dominate the human gut virome, containing over 2,800 species of phages between them.

“The complex bacteriophage communities represent one of the biggest gaps in our understanding of the human microbiome. In fact, most studies have focused on the dysbiotic process only in bacterial populations,” write the authors of the new study.

Specifically, the scientists showed that volunteers with increased Caudovirales levels in the gut microbiome performed better in executive processes and verbal memory. In comparison, the data showed that increased Microviridae levels impaired executive abilities. Simply put, there seems to be an association between this type of gut biome and higher cognitive functions.

These two prevalent bacteriophages run parallel to human host cognition, the researchers write, and they may do this by hijacking the bacterial host metabolism.

To reach this conclusion, the researchers first tested fecal samples from 114 volunteers and then validated the results in another 942 participants, measuring levels of both types of bacteriophage. They also gave each volunteer memory and cognitive tests to identify a possible correlation between the levels of each species present in the gut virome and skill levels.

The researchers then studied which foods may transport these two kinds of phage into the human gut -results indicated that the most common route appeared to be through dairy products.

They then transplanted fecal samples from the human volunteers into the guts of fruit flies and mice – after which they compared the animal’s executive function with control groups. As with the human participants, animals transplanted with high levels of Caudovirales tended to do better on the tests – leading to increased scores in object recognition in mice and up-regulated memory-promoting genes in the prefrontal cortex. Improved memory scores and upregulation of memory-involved genes were also observed in fruit flies harboring higher levels of these phages.

Conversely, higher Microviridae levels (correlated with increased fat levels in humans) downregulated these memory-promoting genes in all animals, stunting their performance in the cognition tests. Therefore, the group surmised that bacteriophages warrant consideration as a novel dietary intervention in the microbiome-brain axis.

Regarding this intervention, Arthur C. Ouwehand, Technical Fellow, Health and Nutrition Sciences, DuPont, who was not involved in the study, told Metafact.io:

“Most dietary fibres are one way or another fermentable and provide an energy source for the intestinal microbiota.” Leading “to the formation of beneficial metabolites such as acetic, propionic and butyric acid.”

He goes on to add that “These so-called short-chain fatty acids may also lower the pH of the colonic content, which may contribute to an increased absorption of certain minerals such as calcium and magnesium from the colon. The fibre fermenting members of the colonic microbiota are in general considered beneficial while the protein fermenting members are considered potentially detrimental.”

It would certainly be interesting to identify which foods are acting on bacteriophages contained within our gut bacteria to influence cognition.

Despite this, the researchers acknowledge that their work does not conclusively prove that phages in the gut can impact cognition and explain that the test scores could have resulted from different bacteria levels in the stomach but suggest it does seem likely. They close by stating more work is required to prove the case.

How ancient gut microbes might have shaped human evolution

Humans are, in fact, mostly microbes. There are over 100 trillion microbes living inside the human body, which outnumber our human cells ten to one. Most of these microbes live inside the gut, particularly in the large intestine, and are collectively known as the ‘microbiome’. According to a new study, the microbiome may have played a critical role in our ancestors’ quest to spread across the world, allowing them to survive in new geographical areas.

“In this paper, we begin to consider what the microbiomes of our ancestors might have been like and how they might have changed,” Rob Dunn of the North Carolina State University and lead author of the new study said in a statement. “Such changes aren’t always bad and yet medicine, diet, and much else makes more sense in light of a better understanding of the microbes that were part of the daily lives of our ancestors.”

Dunn and colleagues analyzed data gathered by other studies, comparing the microbiota among humans, apes, and other non-human primates.

The bacteria in the microbiome help digest our food, regulate our immune system, protect against other bacteria that cause disease, and produce vitamins including B vitamins B12, thiamine and riboflavin, and Vitamin K, which is needed for blood coagulation. It was only in the late-1990s that the existence of the microbiome was generally recognized.

The new study’s results suggest an extraordinary variation in the composition and function of human gut microbes depending on a person’s lifestyle and geographical location. It would mean that our gut microbes have had to adapt to new environmental conditions and likely did so quickly.

When our ancestors migrated to a new region, they not only encountered novel climates and habitats, but also new kinds of foods and diseases.

By having an adaptive microbiome, these ancestors could digest novel foods that they encountered in a local region while also increasing their resilience against new diseases.

As such, the authors concluded in the journal Frontiers in Ecology and Evolution that microbial adaptation might have been critical to facilitating the spread of humans in a range of environments.

Such microbial adaptations were easily transmitted from human to human thanks to the tight-knit social structure. Yet, our ancestors not only shared microbes among themselves, but they also outsourced them into food through fermentation.

By fermenting food, human ancestors virtually extended their guts outside of their bodies as microbes allowed digestion to begin externally.

Fermentation allowed humans to store food for long periods of time and stay in one place, facilitating larger communities. Fermented foodstuff also re-inoculated the consumers, ensuring that in time their microbiota became more similar to each other compared to individuals living in other groups. So, in many ways, the story of human evolution is very much intertwined with that of microbes.

“We outsourced our body microbes into our foods. That could well be the most important tool we ever invented. But it is a hard tool to see in the past and so we don’t talk about it much,” says Dunn. “Stone artifacts preserve but fish or beer fermented in a hole in the ground doesn’t”.

The authors caution that their hypothesis needs to be validated by further studies, preferably performed by an interdisciplinary team made of paleoanthropologists, medical researchers, ecologists and more.

“We are hoping the findings will change some questions and that other researchers will study the consequences of changes in the human microbiome,” says Dunn. “Hopefully the next decade will see more focus on microbes in our past and less on sharp rocks.”

Sunlight might affect gut microbiome diversity

Researchers at the University of British Columbia in Canada have found a significant link between exposure to ultraviolet rays and an increase in gut bacterial diversity. The findings could prove important in managing autoimmune diseases known to be associated with gut bacterial diversity, such as inflammatory bowel disease.

Credit: Pixabay.

Ultraviolet (UV) designates a band of the electromagnetic spectrum with wavelengths ranging from 10 nm to 400 nm, shorter than that of visible light but longer than X-rays. Our senses cannot detect UV rays — not until the damage is done — which is why they can be especially dangerous. Too much time in the sun causes sunburns, eye damage, accelerate aging, and skin cancer.

There are 2 main types of UV rays that interact with our skin.

  • UVB, which is responsible for the majority of sunburns, and
  • UVA, which penetrates deep into the skin. It ages the skin, but contributes much less towards sunburn.

Although prolonged exposure to UV radiation can be very harmful, we also require moderate exposure in order to live healthily. Research has shown a link between UV exposure and the synthesis of vitamin D, which promotes the formation and strengthening of bones (a deficiency will cause bone softening diseases, which then causes rickets in children and osteomalacia in adults), strengthens the immune system, and offers protection against some cancers.

In the study, 21 female participants received three 60-second full-body UVB exposure sessions over the course of one week. The researchers drew blood and fecal samples from each subject at the beginning and end of the trial in order to analyze changes in vitamin D and gut bacteria. Half of the participants had taken vitamin D supplements during the prior three winter months.

The subjects who didn’t take vitamin D supplements experienced an increase in alpha and beta gut microbiome diversity. They also experienced a 10% increase in blood serum vitamin D concentration after the week-long UVB exposure. On the other hand, those who took vitamin D supplements did not experience an increase in gut microbiome diversity. This suggests that vitamin D is the mediating factor between UVB exposure and gut microbial activity.

“Prior to UVB exposure, these women had a less diverse and balanced gut microbiome than those taking regular vitamin D supplements,” says lead-author Bruce Vallance, from the University of British Columbia. “UVB exposure boosted the richness and evenness of their microbiome to levels indistinguishable from the supplemented group, whose microbiome was not significantly changed.”

Although the researchers haven’t identified a formal mechanism, they think that the initial exposure to UVB light alters the immune system — first at the level of the skin, then more systematically throughout the body, affecting how bacteria interact with the environment inside the intestines. Previously, studies have shown that inflammatory bowel disease symptoms can worsen when the body experiences vitamin D deficiency, which strengthens the idea sunlight exposure and gut health are somewhat connected.

Next, the team plans on performing similar studies on a larger cohort of subjects in order to investigate this link better.

“The results of this study have implications for people who are undergoing UVB phototherapy, and identifies a novel skin-gut axis that may contribute to the protective role of UVB light exposure in inflammatory diseases like MS and IBD,” says Vallance.

The findings appeared in the journal Frontiers in Microbiology.

Credit: Pixabay.

Drinking red wine (in moderation) improves gut health

Credit: Pixabay.

Credit: Pixabay.

A new study found that people who drank red wine had more bacterial diversity in their guts — which is seen as a sign of better gut health — compared to non-drinkers. Red wine drinkers also showed lower levels of obesity and ‘bad’ cholesterol.

Researchers at King’s College London studied the association between gut microbiome and general health in a group of 916 British female twins who either drank beer, cider, red wine, white wine, or spirits. Additionally, there were three other cohorts in the UK, the U.S., and the Netherlands, bringing the total study participants to over 4,000.

Gut bacteria + red wine = <3

People tend to see bacteria as harmful and potentially dangerous to our health — but that is not necessarily so.

The gut microbiota (also called the gut microbiome, and previously called the gut flora) is the name given to the microbe population living in our intestine. Our gut is home to trillions of microorganisms from hundreds of different species, totaling 3 million genes — 150 times more than human genes. Each one of us carries around 2% of our overall body weight in bacteria

Increasingly, the gut microbiome has been shown to be important in a number of diseases, including your weight, general health, and even mental health.

In general, scientists believe that the higher the number of different bacterial species in a person’s gut, the better the health outcomes. And this is exactly what they found for people who consumed red wine. Those who drank beer, white wine, or spirits did not show a more diverse gut microbiome.

“Although we observed an association between red wine consumption and the gut microbiota diversity, drinking red wine rarely, such as once every two weeks, seems to be enough to observe an effect. If you must choose one alcoholic drink today, red wine is the one to pick as it seems to potentially exert a beneficial effect on you and your gut microbes, which in turn may also help weight and risk of heart disease. However, it is still advised to consume alcohol with moderation,” said Dr. Caroline Le Roy from King’s College London, first author of the study.

The reason why red wine may improve gut health may be due to the many polyphenols it contains. Polyphenols are natural compounds also present in fruits and vegetables which have many beneficial properties — they’re a great source of antioxidants, for instance — and may act as a fuel source for the gut bacteria.

“This is one of the largest ever studies to explore the effects of red wine in the guts of nearly three thousand people in three different countries and provides insights that the high levels of polyphenols in the grape skin could be responsible for much of the controversial health benefits when used in moderation,”Professor Tim Spector from King’s College London said in a statement.


Over 100 new species of bacteria discovered in your gut

An international research team has created the most comprehensive record of human intestinal flora to date. Over 100 of the species they list are completely new to science.


Image via Pixabay.

Our intestinal microbiome is essential in keeping us healthy, well-fed, and in good spirits. Each one of us carries around 2% of our overall body weight in bacteria. However, we don’t have a very clear idea of what strains call our innards ‘home’. A new study, published by researchers from the Wellcome Sanger Institute, Hudson Institute of Medical Research, Australia, and EMBL’s European Bioinformatics Institute comes to flesh out our understanding of these bugs with the most comprehensive look at human intestinal flora to date.

The resource will allow scientists to better understand our bacterial compadres and make it easier to analyze the particular microbiome of each individual. All in all, the team hopes their work will point the way towards new treatments for diseases such as gastrointestinal disorders, infections, and immune conditions.


“This study has led to the creation of the largest and most comprehensive public database of human health-associated intestinal bacteria,” says first author Dr Samuel Forster from the Wellcome Sanger Institute.

“The gut microbiome plays a major in health and disease. This important resource will fundamentally change the way researchers study the microbiome.”

The team worked with fecal samples collected from 20 people in the UK and Canada. They isolated, grew, and DNA-sequenced 737 individual strains of bacteria from this material. Further analysis showed these strains make up 273 separate bacterial species — strains are roughly equivalent to a sub-species — including 173 that have never before been sequenced. Of these latter ones, 105 have never been isolated before.

So why is that important? Well, when researchers need to study the effect of microbiomes on human health, they usually sequence the DNA of the whole sample (which is to say, the genomes of all species in a sample), and then try to tease apart its different component species. It works really well if you know what each individual species’ genome looks like — however, we didn’t have reference material for all the inhabitants of our bellies. That’s where the present study comes into the picture.

The data collected by the team will make it cheaper, faster, and easier for researchers to determine which bacteria are present in a certain community, and to research their role in diseases. If researchers need to check a particular hypothesis — that certain bacteria increase in the case of a disease, for example — they can get an isolate from the collection and run it through tests in the lab. Up to now, researchers would have to obtain stool samples from which to isolate particular strains or species — which took a lot of time and incurred costs.

“For researchers trying to find out which species of bacteria are present in a person’s microbiome, the database of reference genomes from pure isolates of gut bacteria is crucial,” says coauthor Dr Rob Finn from EMBL’s European Bioinformatics Institute.

“This culture collection of individual bacteria will be a game-changer for basic and translational microbiome research,” adds senior author Dr Trevor Lawley (also from the Wellcome Sanger Institute). “Ultimately, this will lead us towards developing new diagnostics and treatments for diseases such as gastrointestinal disorders, infections and immune conditions.”

The paper “Human Gastrointestinal Bacteria Genome and Culture Collection” has been published in the journal Nature Biotechnology.

Immigrating drastically changes people’s microbiome

As soon as a person immigrates to the US, their microbiome starts to change.

People switching from a Thai diet to an American diet exhibit a drastic reduction in microbiome diversity. Depicted here: a Thai dish (fish in chili sauce).

Immigration is a touchy subject in many parts of the world, but while some things are debatable, researchers found clear signs that the microbiome of immigrants drastically changes when they come to the US. Specifically, researchers from  the University of Minnesota and the Somali, Latino, and Hmong Partnership for Health and Wellness have studied communities migrating from Southeast Asia to the US, finding that their gut biome is immediately “Americanized.”

“We found that immigrants begin losing their native microbes almost immediately after arriving in the U.S. and then acquire alien microbes that are more common in European-American people,” says senior author Dan Knights, a computer scientist and quantitative biologist at the University of Minnesota. “But the new microbes aren’t enough to compensate for the loss of the native microbes, so we see a big overall loss of diversity.”

It has to be said that this isn’t really a good thing. Generally speaking, microbiomes from the Western world are associated with greater obesity, whereas people from developing countries tend to have more diverse and healthy microbiomes (particularly in areas where fruits and vegetables are more popular). It seems quite normal that a person’s biome would shift when the diet changes, but it’s striking to see how much diversity is lost, and how fast this happens — in only six to nine months.

“Obesity was a concern that was coming up a lot for the Hmong and Karen communities [from Thailand] here. In other studies, the microbiome had been related to obesity, so we wanted to know if there was potentially a relationship in immigrants and make any findings relevant and available to the communities. These are vulnerable populations, so we definitely try to make all of our methods as sensitive to that as possible and make sure that they have a stake in the research,” says first author Pajau Vangay.

[panel style=”panel-default” title=”Good microbes” footer=””]The gut microbiota (also called the gut microbiome, and previously called the gut flora) is the name given to the microbe population living in our intestine. Essentially, our gut contains trillions of microorganisms, from hundreds of different species, containing 3 million genes — 150 times more than human genes.

These are, essentially, “good” microbes — at least some of them.

Increasingly, the gut microbiome has been shown to be important in a number of diseases, including your weight, general health, and even mental health. [/panel]

The team compared the microbiome of Thai immigrants to people who were still living in Thailand. The study also featured the children of those immigrants, as well as Caucasian American controls. Researchers were also able to follow a group of 19 Karen refugees as they relocated from Thailand to the US, allowing them to see how the microbiomes were changing in time.

Significant changes took place quite fast. Most notably, a Western strain of bacteria (Bacteroides) began to displace the non-Western bacteria strain (Prevotella). The kids’ biomes changed significantly faster than those of the adults.

Overall, the changes seem to be a logical consequence of a change in diet, but they are still concerning.

“When you move to a new country, you pick up a new microbiome. And that’s changing not just what species of microbes you have, but also what enzymes they carry, which may affect what kinds of food you can digest and how your diet interacts with your health,” he says. “This might not always be a bad thing, but we do see that Westernization of the microbiome is associated with obesity in immigrants, so this could an interesting avenue for future research into treatment of obesity, both in immigrants and potentially in the broader population.”

While no direct cause-effect has been established between a Western diet and obesity and other health issues, there is a lot of correlation between the two. Migration from a non-western nation to the United States is associated with a loss in gut biome diversity, which may predispose individuals to metabolic diseases, researchers conclude.

“We don’t know for sure why this is happening. It could be that this has to do with actually being born in the USA or growing up in the context of a more typical US diet. But it was clear that the loss of diversity was compounded across generations. And that’s something that has been seen in animal models before, but not in humans,” says Knights.

The study was published in Cell. http://dx.doi.org/10.1016/j.cell.2018.10.029

Weight gain is mostly controlled by what you eat — not genetics

If you want to blame someone for those extra pounds, the best place to look is probably in the mirror.

As the world tries to deal with its ever-growing obesity crisis, the main causes of this problem are still under debate. However, more and more studies are indicating that the main culprit is, as expected, food.

Genes decide a lot of things about your body — your eye color, your hair, even how you look like. But, according to a new study, it doesn’t really decide how much you weigh (as an adult, at least). Scientists at King’s College London recently carried out a study on twins to assess how the gut processes and distributes fat.

Essentially, they analyzed poop samples from over 500 pairs of twins to build up a picture of how the gut microbiome distributes fat. They also analyzed how much of this process is genetic and how much is directed by environmental factors. Overall, they found that only 17.9% of all gut processes could be attributed to hereditary factors, while 67.7% of gut activity was influenced by environmental factors — mainly, the regular diet.

This is an exciting study, not just because it confirms that what we eat governs how our weight is distributed, but because it allows researchers to understand which microbes are associated with which chemical metabolites in the gut. Ultimately, this could help scientists understand how the gut bacteria affects us, and how it can be modified for weight management.

The fecal metabolome largely reflects gut microbial composition, and it is strongly associated with visceral-fat mass, thereby illustrating potential mechanisms underlying the well-established microbial influence on abdominal obesity. Dr. Jonas Zierer, the lead author of the study, believes this could one day be instrumental in dealing with obesity.

‘This study has really accelerated our understanding of the interplay between what we eat, the way it is processed in the gut and the development of fat in the body, but also immunity and inflammation. By analysing the faecal metabolome, we have been able to get a snapshot of both the health of the body and the complex processes taking place in the gut.’

This is also good news because it means that most of the factors associated with extra pounds are modifiable. Zierer adds:

‘This new knowledge means we can alter the gut environment and confront the challenge of obesity from a new angle that is related to modifiable factors such as diet and the microbes in the gut. This is exciting, because unlike our genes and our innate risk to develop fat around the belly, the gut microbes can be modified with probiotics, with drugs or with high fibre diets.’

Head of the Department of Twin Research at King’s, Professor Tim Spector was also excited by the possibility. He emphasizes another advantage of this study — the fact that potential treatments or supplements might be implemented at a large scale through innovative approaches.

‘This exciting work in our twins shows the importance to our health and weight of the thousands of chemicals that gut microbes produce in response to food. Knowing that they are largely controlled by what we eat rather than our genes is great news, and opens up many ways to use food as medicine. In the future these chemicals could even be used in smart toilets or as smart toilet paper.’

Worldwide, over 2 billion people are overweight or obese, and over the past 20 years, obesity rates have more than doubled. The growing trend shows no sign of stopping or slowing down, as childhood obesity also grows at dramatic rates: 1000% in the past 40 years.

Journal Reference: Zierer et al. “The fecal metabolome as a functional readout of the gut microbiome.” Nature Genetics (2018). https://doi.org/10.1038/s41588-018-0135-7

Lab mice with natural gut bacteria are wildly more resistant to disease and tumors

For medication or vaccines to be okayed for use on humans, they first need to be extensively tested in the lab. Drugs need to be tested in living organisms, which is very different than in a petri dish because there are more complex interactions. Often, they are tested on mice, which are the prime model of human disease because they share 99% of our genes and are cheap and easy to test in the lab. However, sometimes, vaccine studies have wildly different results in mice, humans, and other animals. That could be due to the contents of mice guts, a new study reports. The lack of exposure to enough healthy bacteria may leave the immune system of lab mice compromised and not such a good model for human disease.

The lab mouse strain C57BL/6 that was used for this study. Image credits: Wualex.

Natural is better

Laboratory mice have been bred to be genetically similar for reproducible results. In addition, the mice spend their entire lives in the lab and live mostly in sterilized environments. They are not exposed to the same bacteria that wild mice would be exposed to. These bacteria make up the microbiome, which is important in digestion and the immune system. As such, lab mice do not react to medication the same way that mice with a healthy community of gut bacteria would. In the same vein, humans don’t live in a sterilized box and have a more varied microbiome than lab mice and perhaps the reactions are not comparable.

Researchers from the National Institute of Diabetes and Digestive and Kidney Diseases tested how lab mice with a more natural microbiome would respond to diseases. They trapped closely related wild mice and sampled their bacterial gut microbiomes. Indeed, the wild mice had different gut biota than the laboratory mice. They took pregnant germ-free mice and they gave some of them a lab mouse microbiome and some a wild mouse microbiome and raised them over several generations. After four generations, the descendants had the same microbiomes as their ancestors were given.

A diagram showing the difference between a wild and lab lab mouse, and the hybrid that was created for this study. Image credits: Credit: Rosshart et al.

“We think that by restoring the natural ‘microbial identity’ of laboratory mice, we will improve the modeling of complex diseases of free-living mammals, which includes humans and their diseases,” said Barbara Rehermann, M.D., chief of the Immunology Section, Liver Diseases Branch, of the NIH’s National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK).

When exposed to the influenza virus, 92% of the mice with wild biomes survived while only 17% of control mice survived. They also had fewer tumors and less severe disease in the face of induced colorectal tumors. Reduced inflammation was observed in both cases. The wild microbiome could then be added to disease testing as an additional component. It could also explain why certain results in mice are not reproducible between labs, despite using the same strain of mice and other conditions. The microbiome may influence infection and drug response. This new model with “wild” gut bacteria seems to be more predictive for free-living mammals than current models. It shows the protective mechanisms that living creatures have that are relevant in the natural world.

Future outlook

Although not a goal of the study, it brings up another parallel between mice and men. The lab mice raised in a sterile environment were more vulnerable to disease and cancers. Children that are raised with few germs in the house have a higher chance of developing allergies and asthma. To some degree living in a germ-free or intensely disinfected house in addition to not spending much time outside lowers the number of healthy bacteria and keeps a healthy, diverse microbiome from forming. Perhaps now, or in the future, our ability to respond to diseases will diminish due to an unhealthy microbiome.

This study is not saying that all mouse-based studies are now rubbish. It is adding an extra tool to use in mouse-based research, in particular, for specific research questions.

“We do not intend to propose a general switch to natural microbiota in all types of studies. We rather think, that future research should aim to use microbiota tailored to specific research questions. For example, our findings are relevant in the context of the hygiene hypothesis, in that early exposure to inflammatory stimuli that are abundant in the natural world, has beneficial effects. We think that “natural microbiota” may be a valuable tool to further probe the hygiene hypothesis in regards to many unanswered questions (e.g. auto-immune diseases, autoimmunity, allergies etc..),” said Stephan Rosshart, M.D., first author of the paper and NIDDK postdoctoral fellow to ZMEScience.

Additionally, this new model is important for preclinical medical studies to try to better reflect real-world conditions. It could model human reactions to certain medications and treatment, and lead to new therapies. For example, changing the microbiome or imitating the same pathways may become a disease treatment. This study opens up many, interesting new directions to explore.

Journal reference: Rosshart et al. Wild Mouse Gut Microbiota Promotes Host Fitness and Improves Disease Resistance. Cell, 2017 DOI: 10.1016/j.cell.2017.09.016



DNA strands.

Blood DNA sequencing reveals there’s a lot more microbes living inside you — and we’ve never seen over 99% of them before

A new paper looking at the DNA fragments floating around in human blood reports that there are way more microbes living inside us than we thought — and we’ve never seen most of them before.

DNA strands.

Image credits Colin Behrens.

The idea behind this paper started taking shape as a team led by Stephen Quake, a professor of bioengineering and applied physics, a member of Stanford Bio-X and the paper’s senior author, were looking for a new non-invasive method to determine the risk of rejection in transplant patients. This is traditionally done using a biopsy, which involves a very large needle and quite a bit of ‘ow’.

Needless to say, nobody was very big on the procedure. So Quake’s lab wanted to see if they can work around the issue by looking at the bits of DNA floating around in patients’ blood — what’s known as cell-free DNA. The team expected to find the patient’s DNA, the donor’s DNA, and genetic material from all the bacteria, viruses, and all the other critters that make up our personal microbiome. A spike of donor DNA would, in theory, be one of the first signs of organ rejection.

But what the team didn’t expect to find was the sheer quantity and diversity of microbiome-derived DNA in the blood samples they used.

Bugs galore

“We found the gamut,” says professor Quake. “We found things that are related to things people have seen before, we found things that are divergent, and we found things that are completely novel.”


Throughout their project (which spanned several studies), the team gathered samples from 156 heart, lung, and bone marrow transplant recipients, and 32 from pregnant woman — pregnancy also has a huge effect on the immune system, similar to immunosuppressants, although we don’t really know how.

Of all the non-human DNA bits found in these samples, a whopping 99% couldn’t be matched to anything in existing genetic databases. In other words, they came from strains we didn’t even know existed. So the team went to work on characterizing all that genetic material. According to them, the “vast majority” falls into the phylum proteobacteria. The largest single group of viruses identified in this study belong to the torque teno family (TTVs). In fact, Quake says their work has “doubled the number of known viruses in that family” in one fell swoop.

Known torque teno viruses infect either animals or humans, but many of the TTVs the team identified don’t fit in either group.


“We’ve now found a whole new class of human-infecting ones that are closer to the animal class than to the previously known human ones, so quite divergent on the evolutionary scale,” Quake adds.

The team believes that we’ve missed all these microbes up to now because narrow studies, by their very nature, miss the bigger picture. Researchers often focus their attention on a few interesting microbes and glance over everything else. Blood samples, by contrast, allowed them to look at everything swimming around inside of us, instead of looking at a few individual pieces. It was this net-cast-wide approach — which the team humorously refer to as a “massive shotgun sequencing” of cell-free DNA — that allowed the team to discover how hugely diverse human microbiomes are.

In the future, the team plans to take a similar look at other animals to see what species their microbiomes harbor.

“There’s all kinds of viruses that jump from other species into humans, a sort of spillover effect, and one of the dreams here is to discover new viruses that might ultimately become human pandemics,” Quake says.

“What this does is it arms infectious disease doctors with a whole set of new bugs to track and see if they’re associated with diseases. That’s going to be a whole other chapter of work for people to do.”

The paper “Numerous uncharacterized and highly divergent microbes which colonize humans are revealed by circulating cell-free DNA” has been published in the journal Proceedings of the National Academy of Sciences.


We still don’t know which gut bacteria is beneficial, but scientists have some good hints

There are ten times more bacteria in your body than your own cells. This might seem scary, but really you wouldn’t be able to function without most of them like the probiotics that help digest your food and fight invading microbes. There’s good bacteria and bad bacteria, but the gut seems to be so diverse in its bacterial offering from person to person that scientists have always found it difficult to say “hey, this is what a healthy microbiome should look like.” Analyzing thousands of bacteria species in your guy is challenging and we’re still not there, but a recent effort involving 4,000 participants has some good hints as to what makes a healthy gut.


Image: Pixabay

Researchers collected and analyzed feces from 4,000 individuals living in the U.S., the United Kingdom, Belgium and the Netherlands. They identified 664 different genera, although we’re pretty convinced there are plenty more bacterial species which weren’t tagged. Later, the stool samples were expanded to include some coming from Papua New Guinea, Peru and Tanzania. In this expanded version, the researchers found 14 genera of microbes that were common in  95% of the humans sampled.

“We compared all the microbiota we could get our hands on,” says Jeroen Raes at the University of Leuven (KUL) in Belgium, who led the study.

This bacteria diversity data was then correlated with the health and behaviour of the participants. The most important takeaway is having  bacterial diversity in the gut offers health benefits, and the more the better. Those people who had less microbiome diversity were those with a higher body-mass index, which corresponds to being overweight or obese. Those who had the most gut bacteria diversity ate a lot of fruits and vegetables. Dairy-rich diets were also associated with a more diverse biome. Subjects who drank coffee and tea also saw an improvement, while soda reduced the diversity for unclear reasons.

To increase your gut bacteria diversity, the findings suggests, consume fruits, vegetables, dairy and probiotics-rich products like yoghurt.

The older the people involved in the study, the more diverse their biomes. More than anything, however, the use of medicine influenced the greatest variation among the people involved in this study. These include drugs like antibiotics, osmotic laxatives, medications for inflammatory bowel disease, benzodiazepines, antidepressants, antihistamines or hormones used for birth control or to alleviate symptoms of menopause.

Considering so few genera were shared by people across the world, the relationship between a certain bacterial biome and health benefits is debatable. We know for sure, however, that there are bacteria that cause a plethora of health problems like irritable bowel syndrome, and even as many as 23,000 deaths in the United States alone. Through careful analysis and more genetic sequencing of the bacteria that line our guts, many lives might be saved.

Your microbial cloud is your “signature”

New research focused on the personal microbial cloud. (Credit: Viputheshwar Sitaraman, of Draw Science)

New research focused on the personal microbial cloud. (Credit: Viputheshwar Sitaraman, of Draw Science)

Humans are walking ecosystems. Each of us carries around about 100 trillion microbes in and on our bodies, which make up our microbiome. The quality of this bacterial community has a lot to say about our health and well-being. The blend of microbes is also surprisingly unique, which says a lot about who we are as individuals.

New research published in the September 22 issue of PeerJ has found that people can be identified by the nature of the microbial cloud that they release in the air around them. We each have our own microbial “signature.”

A not-so-empty room

Scientists have already amassed plenty of information about the human microbiome and they already know that people disperse some of those bacteria to their environments. These microbes come primarily from dust, our clothing, and our bodies.

Two new experiments, conducted at the University of Oregon, investigated the individual nature of these bacterial clouds.

The first experiment was designed to test whether researchers could confirm the presence of a person based only on bacterial traces. The researchers asked study participants to sit alone in a sanitized chamber that was filled with filtered air. A second, unoccupied chamber was used as a sterile control.

Each participant was given a clean outfit to wear to reduce the number of particles coming from clothing. Participants also sat in a plastic chair that had been disinfected and were given a disinfected laptop to use for communication and for personal entertainment during the study.

The experiment involved three participants, each tested for a total of six hours. Air in the test chamber was compared to the air in the unoccupied chamber. Any particles that came from a participant were filtered out of the chamber air and genetically sequenced to identify the mix of bacteria. The analyses involved thousands of different bacteria types in over 300 air and dust samples.

The researchers were able to determine that a person was present in the chamber after two hours, based only at the presence of bacteria in the air samples. They also found, however, that they could distinguish one person from another based on the unique combinations of bacteria from each participant.

This result motivated a second, more precise experiment.

Eight new people were asked to sit alone in the chamber for two 90-minute sessions. Analyzing the bacteria in the air revealed several individual features of each participant, including whether the person was male or female.

“We expected that we would be able to detect the human microbiome in the air around a person,” said lead author James Meadow, who was a postdoctoral researcher at the University of Oregon from the Biology and the Built Environment Center at the University of Oregon.at the time of the study. “But we were surprised to find that we could identify most of the occupants just by sampling their microbial cloud.”

A few bacteria groups, such as Streptococcus (commonly found in the mouth), Propionibacterium and Corynebacterium

(found on the skin), were primary indicators in the study. While these microbes are common in humans, it was the different combinations of these bacteria populations that distinguished between individuals.

Subtle differences were also found in the microbial clouds. Some people, for example, gave off different amounts of bacteria to the air due to such personal habits as how much they scratched and how much they fidgeted.

Tracking individual biology

The demonstration that bacteria clouds can be traced to individuals could shed light on how infectious diseases spread in buildings.

The results could also have a forensic use. Bacterial residue in the air might, for example, be used to determine where a person has been, even after they’ve left a space. The contributions of other people – or even animals – in those spaces, however, could easily complicate any analysis, so forensic uses will likely require more research.

Many things are used to detect and identify us in modern life. Now we know that the bacteria on, in, and around each of us has a close connection to the places we occupy, can be detected even after we’re gone . . . . and can be traced back to us.



Primary Source: New research finds that people emit their own personal microbial cloud


Social interactions and the microbiome

The microbiome, or the collection of bacteria living inside humans and other organisms, is an important topic in research today, because many scientists have made connections between different diseases and illness to the populations of bacteria inside us, specifically in our guts. Previously, ZME Science has covered what the microbiome is  and several important studies.

There are still many questions about the microbiome, because diet, genetics, location, and lifestyle all play a role in what species are dominant or absent and how well they grow inside us. Performing studies outside a lab is particularly difficult since it is hard to isolate one of those factors and study how the populations change.

Image via Amboseli Baboons.

Dr. Jenny Tung and her research team examined the microbiome and how a social network affected the populations of bacteria of Amboseli baboons of Kenya. Previously, these baboons were studied in their natural habitat, and observed for extended period of time by a different research group. There were a total of 48 baboons that naturally existed in two different groups, Mica’s group and Viola’s group. The baboons in each group groom each other, and how frequently this behavior was observed and between which pair was documented for a year. For an entire month, feces samples were collected from each animal. From these samples, shotgun metagenomic sequencing was applied, and this method cleaves the genetic material found in the sample and sequences the fragments. The fragments tell researchers what kind of bacteria there is and what kind of chemical processes are happening.

The authors state:

“Our results argue that social interactions are an important determinant of gut microbiome composition in natural animal populations – a relationship with important ramifications for understanding how social relationships influence health, as well as the evolution of group living.”

They found that social group was more important to predicting the species of bacteria than sex or age. Since Mica and Violas’s group lived in the same habitat and their diets were essentially the same, these factors could not explain why the microbiomes were different.

They also found that the baboons in the same group that groomed each other more frequently had more similar microbiomes, both in terms of what species of bacteria are present and how large the population is. A potential explanation for this is that this pair of baboons ate more similarly than the rest of the group. This potential explanation was taken into account using statistical tests, but these statistical tests ultimately did not produce any results that suggested the microbiome composition changes were due to grooming partner’s diets.

Though this study represents important new findings for the microbiome, we still do not understand how this works. Researching more about how the social network changes the populations of microbes inside us could help us understand both evolution and disease better.[1]


[1] Tung, Jenny, Luis B Barreiro, Michael B Burns, Jean-Christophe Grenier, Josh Lynch, Laura E Grieneisen, Jeanne Altmann, Susan C Alberts, Ran Blekhman, and Elizabeth A Archie. “Social Networks Predict Gut Microbiome Composition in Wild Baboons.” ELife (2015). Web. 15 June 2015.


Scientist gives himself Fecal Transplant from Hunter-Gatherer from Tanzania… to See how it Goes

A field researcher from America has transplanted fecal microbiome from a Tanzanian tribesman to his own gut. Why? Well… to see what happens, basically.

Fecal bacteria, magnified 10,000x Fecal transplant is increasingly accepted as a medical treatment for some diseases. Eric Erbe, digital colorization by Christopher Pooley

Fecal bacteria, magnified 10,000x Fecal transplant is increasingly accepted as a medical treatment for some diseases. Eric Erbe, digital colorization by Christopher Pooley

“AS THE SUN set over Lake Eyasi in Tanzania, nearly thirty minutes had passed since I had inserted a turkey baster into my bum and injected the feces of a Hadza man – a member of one of the last remaining hunter-gatherers tribes in the world – into the nether regions of my distal colon.”

It’s not every day you get the chance to read an essay which starts like this, isn’t it? Yet that’s exactly how Jeff Leach, the man behind this research, starts his story. He has been part of a team working in Tanzania and living side by side with the Hadza, a group of hunter gatherer people. The Hadza live now the same way their ancestors have for thousands or even tens of thousands of years; they are the last full-time hunter-gatherers in Africa. What’s interesting is that the Hadza are not genetically related to any other people, and their language is unique.

The Hadza are also at the mercy of the local weather and climate. Leach’s team has collected numerous (over 2000) samples from humans, animals, and the environment in order to observe how the microbial communities in and around the Hadza change as a result of the weather patterns – especially the six month variation (dry season – wet season).

A Hadza hunting party. Image via The Telegraph

“[The question is] what a normal or healthy microbiome might have looked like before the niceties and medications of late whacked the crap out of our gut bugs in the so-called modern world,” Leach writes.

For this purpose, the Hadza are indeed ideal subjects. They are not stone-age or isolated people – they’ve had plenty of contact with other humans, but they still have the same diet and lifestyle they’ve had for millennia, and almost never use modern medication.

The microbiome in the colon is starting to receive more and more attention – and rightfully so. The health impact it has on our bodies is huge, and has been widely ignored in Western medicine, until recently. Eating “probiotics” and similar foods is a good step, but this just “scratches the surface”. Meanwhile, fecal transplant has been used more and more to treat various afflictions.

“Recent research suggests that use of antibiotics may be fundamentally altering our gut biomes for the worse, increasing rates of allergies, asthma and weight gain. In one recent lab study, introduction of genetically altered gut bacteria prevented mice from getting fat. In another, artificial sweetners altered gut microbes and contributed to obesity and other metabolic disorders in mice, and some correlation to the same effect was found in people”, Popular Science writes.

So understanding how our biome changed as a result of a modern lifestyle could have huge implications for future medicine… but is a fecal transplant really necessary? Leach and his team believe it will greatly accelerate the study. Their results are already interesting, but they want to find out as soon as possible if modern humans can survive with ancient fecal biome.

“On the original question of whether or not the gut microbiome composition of the Hadza changes between wet and dry seasons, our initial – though unpublished data – suggest yes. To our knowledge this is the first study in the world to document this pattern among rural and remote populations. Ecologically speaking, this suggests there may not be one steady state – or equilibrium – for the human gut. It’s moving target with multiple steady states.”, Leach writes further.

Another reason why he is doing this is to test his theory: that we have conducted a biome genocide, basically wiping out most of the bacteria that inhabits our gut. He wants to see what will happen when you get that biome back.

“Microbial extinction [is] something I believe we all suffer from in the western world and may be at the root of what’s making us sick.”

Is there truth to his theories? The fact that he would risk inserting a hunter-gatherer’s feces inside of him seems to indicate that at the very least, he’s very confident in his ideas. Personally, I think what he says makes a lot of sense. Most of what we are is actually bacteria or other foreign bodies – it seems extremely unlikely for those elements to not have any particular impact; wiping them out (as we are doing today, with modern drugs and the modern diet) likely has serious consequences. We’ll keep you posted on how the situation develops.

Source: (Re)Becoming Human: what happened the day I replaced 99% of the genes in my body with that of a hunter-gatherer, by Jeff Leach.


Gut bacteria may control your mind by influencing your dietary choices


Gut bacteria may influence what we want to eat. GIF: University of California

Our gut hosts an enormous population of bacteria, each species with its own niche (they feed on certain foods), which outnumbers our own cells 100-fold. Most of these bacteria are good bacteria, though. In fact, you couldn’t survive without most of them! They’re among the best decomposers, breaking down dead and organic matter otherwise impossible by the gut alone. But while bacteria help us digest food and ward off threatening microbes, it may be the case that bacteria aren’t serving us, but we are serving the bacteria. A recent study which analyzed recent scientific literature found that microbes influence human eating behavior and dietary choices to favor consumption of the particular nutrients they grow best on, rather than passively consuming what they have around.

Our bacterial overlords

It’s yet unclear how the gut microbiome influences our dietary patterns – if the authors are right – but the researchers hypothesize the bacteria must be releasing signaling molecules into our gut. Because the gut is linked to the immune system, the endocrine system and the nervous system, those signals could influence our physiologic and behavioral responses. The research was carried out by scientists at UC San Francisco, Arizona State University and University of New Mexico.

“Bacteria within the gut are manipulative,” said Carlo Maley, Ph.D., director of the UCSF Center for Evolution and Cancer and corresponding author on the paper. “There is a diversity of interests represented in the microbiome, some aligned with our own dietary goals, and others not.”

[ALSO READ] How bacteria colonize the human gut

Fortunately, the researchers write that the relationship goes both ways. Because the bacterial population can evolve and change substance 180 degrees in as little time as 24 hours, we can influence the microbiome by deliberately altering our diet.

“Our diets have a huge impact on microbial populations in the gut,” Maley said. “It’s a whole ecosystem, and it’s evolving on the time scale of minutes.”

Research shows that bacteria may be affecting our eating decisions in part by acting through the vagus nerve, which connects 100 million nerve cells from the digestive tract to the base of the brain. By altering the neural signals in the vagus nerve, bacteria can influence mood and manipulate behavior by changing taste receptors, producing toxins to make us feel bad, and releasing chemical rewards to make us feel good. For instance, tests on mice showed these became more anxious when exposed to certain strains of bacteria. In humans, one clinical trial found that drinking a probiotic containing Lactobacillus casei improved mood in those who were feeling the lowest.

[MORE] 3-D printed bacteria answers questions

While still to be conclusive, the findings suggest that our gut bacteria greatly influence the decisions we make regarding what goes inside our tummies. Other researchers believe this should be further test out. For instance, the Japanese often include seaweeds in their diets, so they have a specialized bacteria that digest seaweed. Would transplanting Japanese gut bacteria, including seaweed bacteria, cause the person in question to crave for seaweed? It’s a tough question to answer, but with enough scrutiny it might shed further light.

An opportunity to exploit bacteria and fight bad health

In any event, scientists are especially interested in the microbiome because of its enormous potential to influence health. By changing food and supplement choices, ingesting specific bacterial species in the form of probiotics, or by killing targeted species with antibiotics we can purposely balance the bacteria species living inside our guts. This might allow us to lead less obese and healthier lives, according to the authors.

[MUST SEE] Amazing bacteria live on pure energy alone by feeding on electricity directly

During an UCSF experiment, researchers recruited a pair of twins in which one was obese and the other lean. Gut bacteria from the twins was transplanted into mice, coupled with a low-fat diet. Bacteria from the lean twin took over the gut of a mouse that already had bacteria from a fat twin, prompting the mouse to lose weight. Regardless of diet, bacteria from a fat mouse did not take over in a mouse that is thin. This suggests it may be possible to fight obesity simply by changing the microbiome. Microbes are always busy digesting food, but some kinds of bacteria harvest more or less energy than others. In the case of obese individuals, you want those kinds of bacteria that leave fewer calories for you.


“Because microbiota are easily manipulatable by prebiotics, probiotics, antibiotics, fecal transplants and dietary changes, altering our microbiota offers a tractable approach to otherwise intractable problems of obesity and unhealthy eating,” the authors wrote.

Findings were reported in the journal Bioessays.

A section of mouse colon is shown with gut bacteria (outlined in yellow) residing within the crypt channel. Credit: Caltech / Mazmanian Lab

How bacteria colonize the human gut – study reveals important insights

Our bodies are hosts to some hundreds of thousands of bacteria that live in harmony with each other, helping the body be healthy, in return for the food and shelter it provides to these tiny organisms . Collectively, all the microorganisms inside the human body are referred to as the microbiome, most of whom are found in the  gastrointestinal (GI) tract – in particular, the colon. Scientists have known for many years that the bacteria inside our bodies are indispensable for human health, but what has always bothered them is a pestering puzzle that until recently has remained largely unsolved. Considering the gut is such a flexible system where food, fecal matter and other fluids are constantly interchanged, how do bacteria thrive in such a system – namely, how do they manage  stable microbial colonization of the gut?

A recent study performed by researchers at California Institute of Technology (Caltech), led biologist Sarkis Mazmanian, may have finally come up with an answer. After studying one common group of bacteria, the scientists found evidence that  a set of genes is paramount to gut colonization. In addition, the Caltech researchers also found out that the bacteria, some of them at least, are in direct contact with the host body – something that was  unperceivable until of late. These advances in our understanding of how the bacteria inside the gut work and flourish might help scientists devise ways to correct for abnormal changes in bacterial communities—changes that are thought to be connected to disorders like obesity, inflammatory bowel disease and autism.

Colonizing the human gut

A section of mouse colon is shown with gut bacteria (outlined in yellow) residing within the crypt channel. Credit: Caltech / Mazmanian Lab

A section of mouse colon is shown with gut bacteria (outlined in yellow) residing within the crypt channel.
Credit: Caltech / Mazmanian Lab

The focus of the researchers’ experiments was on  a genus of microbes called Bacteriodes,  a group of bacteria that has several dozen species and which can be found in the greatest abundance in the human microbiome. Bacteriodes wasn’t chosen because of its popularity, however, instead because it also makes for an excellent lab  pet – it  can be cultured in the lab (unlike most gut bacteria), and can be genetically modified to introduce specific mutations, fundamental criteria in order to test what effects and consequences these bacteria pose in the human body.

A few different species of the bacteria were added to one mouse, which was sterile (germ-free), to see if they would compete with each other to colonize the gut. They appeared to peacefully coexist, as expected, but then the researchers first  colonized a mouse with one particular species, Bacteroides fragilis, and inoculated the mouse with the same exact species as in the first instance, to see if they would co-colonize the same host.  To the researchers’ surprise, the newly introduced bacteria could not maintain residence in the mouse’s gut, despite the fact that the animal was already populated by the identical species.

“We know that this environment can house hundreds of species, so why the competition within the same species?” says Lead author S. Melanie Lee (PhD ’13), who was an MD/PhD student in Mazmanian’s lab at the time of the research. “There certainly isn’t a lack of space or nutrients, but this was an extremely robust and consistent finding when we tried to essentially ‘super-colonize’ the mice with one species.”

To explain the results, Lee and the team developed what they called the “saturable niche hypothesis.” The idea is that by saturating a specific habitat, the organism will effectively exclude others of the same species from occupying that niche. It will not, however, prevent other closely related species from colonizing the gut, because they have their own particular niches. A genetic screen revealed a set of previously uncharacterized genes—a system that the researchers dubbed commensal colonization factors (CCF)—that were both required and sufficient for species-specific colonization by B. fragilis.

“Melanie hypothesized that this saturable niche was part of the host tissue”—that is, of the gut itself—Mazmanian says. “When she postulated this three to four years ago, it was absolute heresy, because other researchers in the field believed that all bacteria in our intestines lived in the lumen—the center of the gut—and made zero contact with the host…our bodies. The rationale behind this thinking was if bacteria did make contact, it would cause some sort of immune response.”

“We are not alone…”

Upon using advanced imaging techniques and technology to survey colonic tissue in B. fragilis colonized mice, the researchers found a small population of microbes living in tiny pockets called crypts. The discovery is extremely important because it explains how the bacteria protect themselves from the constant flow of matter that passes through the GI tract. An even more important discovery came later on. In order to test if these CCF genes had anything to do with how the bacteria colonize the crypts that shelter them from harm, the researchers injected mutant bacteria (without CCF) into the colons of sterile mice. Those bacteria couldn’t colonize the crypts, proving they’re indispensable to the colonization mechanism of gut bacteria.

“There is something in that crypt—and we don’t know what it is yet—that normal B. fragilis can use to get a foothold via the CCF system,” Mazmanian explains. “Finding the crypts is a huge advance in the field because it shows that bacteria do physically contact the host. And during all of the experiments that Melanie did, homeostasis, or a steady state, was maintained. So, contrary to popular belief, there was no evidence of inflammation as a result of the bacteria contacting the host. In fact, we believe these crypts are the permanent home of Bacteroides, and perhaps other classes of microbes.”

The discovery doesn’t however explain however how other bacteria colonize the gut, considering  they don’t have CCF genes at all. A hypothesis proposed by the Caltech researchers is that  Bacteroides are keystone species—a necessary factor for building the gut ecosystem.

“This research highlights the notion that we are not alone. We knew that bacteria are in our gut, but this study shows that specific microbes are very intimately associated with our bodies,” Mazmanian says. “They are living in very close proximity to our tissues, and we can’t ignore microbial contributions to our biology or our health. They are a part of us.”

The findings appeared in the journal Nature.

Manned Mars mission could stomp on existing Martian life

Humanity has long dreamed of a mission to Mars, but the boots which would take the first steps on the Red Planet could be stomping on all Martian life.

Despite any decontamination process, a swarm of 100 trillion microbes will accompany every astronaut who lands on Mars – as a part of their system. This microbiome provides a number of services to humans, including digestion help and keeping unwanted pathogens at bay – these microbes are a part of you, basically. While they do all sort of good stuff for us, they have the potential to destroy any life on Mars, if any life exists.

“We have the responsibility to Mars, I think — even if it’s just Martian microbes — not to kill them by the act of detecting them,” Cynthia Phillips of the SETI (Search for Extraterrestrial Intelligence) Institute said at the SETICon 2 meeting in June in Santa Clara, Calif.

This problem is impossible to go around.

“If you have human astronauts there,” Phillips added, “there’s no way to sterilize them. They’re spewing out thousands of microbes every second. So it’s a real problem.”

Even though the possibilities for such a mission are decades away, space agencies have already toyed with ways to minimize the contamination risks posed by a potential Mars manned mission, and in fact, they have set a rough protocol in 2008. The Committee on Space Research (COSPAR) advise steering clear of any speciel areas life might proliferate, such as gullies and possible geothermal sites.

“It is understood that when humans go to Mars, there will be a release of microbes from the human habitats and from the humans themselves, and also that humans will inevitably be exposed to Mars materials,” said Cassie Conley, NASA’s planetary protection officer.

This is a risk we have to truly ponder if we intend to send humans to Mars.