kissing chimpanzees

Germy friends may keep social chimps healthy

Spending lots of time in close contact with others can up the risk of catching germs and getting sick. But being social may also help transmit “good” microbes, according to a new study of gut microbiomes in chimpanzees.

Researchers monitored changes in the gut microbes and social behavior of wild chimpanzees over eight years in Gombe National Park, Tanzania. The findings show that the number of bacteria species in a chimp’s GI tract goes up when the chimps are more gregarious.

“One of the main reasons that we started studying the microbiomes of chimpanzees was that it allowed us to do studies that have not or cannot be done in humans.”

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, train the immune system, and fight infections. Reduced gut microbial diversity in humans has been linked to obesity, diabetes, Crohn’s, and other diseases.

“The more diverse people’s microbiomes are, the more resistant they seem to be to opportunistic infections,” says coauthor Andrew Moeller, research fellow at the University of California, Berkeley.

For the study, researchers analyzed the bacterial DNA in droppings collected from 40 chimpanzees between 2000 and 2008. The chimpanzees ranged in age from infants to seniors and identified thousands of species of bacteria thriving in the animals’ guts, many of which are also commonly found in humans, such as species of Olsenella and Prevotella.

They then combined the microbial data with daily records of what the animals ate and how much time they spent with other chimps versus alone.

“Chimpanzees tend to spend more time together during the wet season when food is more abundant,” says coauthor Steffen Foerster, research scientist at Duke University. “During the dry season they spend more time alone.”

Each chimpanzee carried roughly 20 to 25 percent more bacterial species during the abundant and social wet season than during the dry season. But the microbiome differences weren’t solely due to seasonal changes in the fruit, leaves, and insects that make up their diet.

The chimps’ shifts between hobnobbing and loner lifestyles were also important.

[Healthy guts burn more calories during sleep]

Gut bacteria likely pass from chimp to chimp during grooming, mating, or other forms of physical contact, or when they inadvertently step where other chimps have pooped, says coauthor Anne Pusey, chair of Duke’s department of evolutionary anthropology and coauthor of the study published in the journal Science Advances.

The mix of bacteria in the animals’ bowels was just as similar between unrelated individuals as it was between mothers and offspring. This was surprising because infants pick up their first microbiomes from their mother when they pass 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 mom.

Scientists don’t yet know if social networks help maintain gut microbiome diversity in humans.

“One of the main reasons that we started studying the microbiomes of chimpanzees was that it allowed us to do studies that have not or cannot be done in humans,” says study coauthor Howard Ochman of the University of Texas at Austin. “It’s really an amazing and previously underexploited resource.”

Further studies are needed to determine how individual fluctuations in chimpanzee gut microbiome diversity impact their health, Moeller says.

Researchers from the University of Pennsylvania and the University of Minnesota are coauthors of the study. The National Institutes of Health and the National Science Foundation supported the work.

Source: Duke University