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Diverse gut microbes increase infection resistance

Spending time in close contact with others often means risking catching germs and getting sick. But being sociable can also transmit 'good' microbes, finds a study in chimpanzees.

The warm, soft folds of our intestines are home to hundreds of species of bacteria and other microbes that help break down food, synthesize vitamins, and train our immune system to fight infections.

"The more diverse people's microbiomes are, the more resistant they seem to be to opportunistic infections." 

Andrew Moeller, research fellow, University of California, Berkeley, co-author of the study.

For over eight years, researchers monitored changes in the gut microbes and social behavior of wild chimpanzees in the Gombe National Park in Tanzania, before coming to this conclusion. They found that the number of bacteria species in a chimp's GI tract goes up when the chimps are more gregarious. Their work is published in the Jan. 15, 2016 issue of Science Advances.

These results help scientists better understand what factors maintain a healthy gut microbiome, which is important to know as reduced gut microbial diversity in humans is linked to obesity, diabetes, Crohn's and other diseases.

Moeller and colleagues analyzed the bacterial DNA in droppings collected from 40 chimpanzees between 2000 and 2008, from infants to seniors. Thousands of species of bacteria were found to thrive in the animals' guts, many of which are also commonly found in humans. Researchers then combined the microbial data with daily records of what the animals ate, along with how much time they spent with other chimps versus being alone.

"Chimpanzees tend to spend more time together during the wet season when food is more abundant," said Steffen Foerster PhD, research scientist at Duke University and study co-author —"During the dry season they spend more time alone."  Consequently, each chimpanzee carried roughly 20 to 25 percent more species of bacteria during the social wet season than during the dry season. But microbiome differences probably aren't solely due to seasonal changes in diet. The social shifts between hobnobbing and loner lifestyles are also important.

Gut bacteria likely passes from chimp to chimp when grooming, mating or some other physical contact, and even when stepping in other chimps poop, adds co-author Anne Pusey, chair of Duke's department of evolutionary anthropology. The mix of bacteria in the animals' bowels is just as similar between unrelated individuals as between mothers and their offspring. This is surprising as infants pick up their microbiomes from their mother when passing through her birth canal.

The findings suggest that, over a lifetime, social interactions with other chimps are just as important for gut microbial diversity as initial exposure from their mom.

Scientists don't know as yet if social networks help maintain gut microbiome diversity in humans. "One of the main reasons we started studying the microbiomes of chimpanzees was it allowed us to do studies that have not or cannot be done in humans," adds study co-author Howard Ochman PhD, at the University of Texas at Austin.

Andrew Moeller wants to do more studies with chimps to determine if fluctuations in chimpanzee gut microbiome diversity also impact their health.

Animal sociality facilitates the transmission of pathogenic microorganisms among hosts, but the extent to which sociality enables animals’ beneficial microbial associations is poorly understood. The question is critical because microbial communities, particularly those in the gut, are key regulators of host health. We show evidence that chimpanzee social interactions propagate microbial diversity in the gut microbiome both within and between host generations. Frequent social interaction promotes species richness within individual microbiomes as well as homogeneity among the gut community memberships of different chimpanzees. Sampling successive generations across multiple chimpanzee families suggests that infants inherited gut microorganisms primarily through social transmission. These results indicate that social behavior generates a pan-microbiome, preserving microbial diversity across evolutionary time scales and contributing to the evolution of host species–specific gut microbial communities.

Other authors include Michael Wilson of the University of Minnesota and Beatrice Hahn at the University of Pennsylvania's Perelman School of Medicine.

This research was supported by grants from the National Institutes of Health (AI58715 and GM101209) and the National Science Foundation (2011119472, 1407133, IOS-LTREB-1052693).

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Jan 22, 2016   Fetal Timeline   Maternal Timeline   News   News Archive   

Researchers found that individual chimpanzees carried roughly 20 to 25 percent more
bacterial species during food abundant and social wet season, than during dry season.
Image Credit: Public Domain




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