L’étrange flore intestinale des chasseurs-cueilleurs

Can the Bacteria in Your Gut Explain Your Mood? - The New York Times
▻http://www.nytimes.com/2015/06/28/magazine/can-the-bacteria-in-your-gut-explain-your-mood.html?_r=0

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Biologists now believe that much of what makes us human depends on microbial activity. The two million unique bacterial genes found in each human #microbiome can make the 23,000 genes in our cells seem paltry, almost negligible, by comparison. ‘‘It has enormous implications for the sense of self,’’ Tom Insel, the director of the National Institute of Mental Health, told me. ‘‘We are, at least from the standpoint of DNA, more microbial than human. That’s a phenomenal insight and one that we have to take seriously when we think about human development.’’

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At the two-minute mark, a prominent scientist in the audience did a spit take.

‘‘Dr. Lyte,’’ he later asked at a question-and-answer session, ‘‘if what you’re saying is right, then why is it when we give antibiotics to patients to kill bacteria, they are not running around crazy on the wards?’’

#microbiote#santé_mentale

Lifestyle determines gut microbes
▻http://www.eurekalert.org/pub_releases/2014-04/m-ldg041514.php

An international team of researchers has for the first time deciphered the intestinal bacteria of present-day hunter-gatherers

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The research team, composed of anthropologists, microbial ecologists, molecular biologists, and analytical chemists, and led in part by Stephanie Schnorr and Amanda Henry of the Max Planck Institute for Evolutionary Anthropology, compared the Hadza gut microbiota to that of urban living Italians, representative of a “westernized” population. Their results, published recently in Nature Communications, show that the Hadza have a more diverse gut microbe ecosystem, i.e. more bacterial species compared to the Italians. “This is extremely relevant for human health”, says Stephanie Schnorr. “Several diseases emerging in industrialized countries, like IBS, colorectal cancer, obesity, type II diabetes, Crohn’s disease and others, are significantly associated with a reduction in gut microbial diversity.”

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The Hadza gut microbiota is well suited for processing indigestible fibres from a plant-rich diet and likely helps the Hadza get more energy from the fibrous foods that they consume. Surprisingly, Hadza men and women differed significantly in the type and amount of their gut microbiota, something never before seen in any other human population. Hadza men hunt game and collect honey, while Hadza women collect tubers and other plant foods. Though they share these foods, each sex eats slightly more of the foods they target. “The differences in gut microbiota between the sexes reflects this sexual division of labour”, says Stephanie Schnorr. “It appears that women have more bacteria to help process fibrous plant foods, which has direct implications for their fertility and reproductive success.” These findings support the key role of the gut microbiota as adaptive partners during the course of human evolution by aligning with differing diets.

Finally, the Hadza gut microbe community is a unique configuration with high levels of bacteria, like Treponema, that in western populations are often considered signs of disease, and low levels of other bacteria, like Bifidobacterium, that in western populations are considered “healthy”. However, the Hadza experience little to no autoimmune diseases that would result from gut bacteria imbalances. Therefore, we must redefine our notions of “healthy” and “unhealthy” bacteria, since these distinctions are clearly dependent on the environment we live in. Genetic diversity of bacteria is likely the most important criterion for the health and stability of the gut microbiome.

#microbiote