Spending time in close contact with others means risking catching germs and getting sick, but being sociable may also help transmit 'good' gut microbes, a new study on chimpanzees has found.
Researchers monitored changes in the gut microbiomes and social behaviour of chimpanzees over eight years in Tanzania. The number of bacterial species in a chimp's gastrointestinal tract (GIT) increased when the chimps were more gregarious.
"The more diverse people's microbiomes are, the more resistant they seem to be to opportunistic infections," said Andrew Moeller from the University of California, Berkeley in US.
The warm, soft folds of our intestines are home to hundreds of species of bacteria and other microbes that help break down food, synthesise 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, researchers said.
They analysed the bacterial DNA in droppings collected from 40 chimpanzees between 2000 and 2008. The chimpanzees ranged in age from infants to seniors.
Researchers 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. During the dry season they spend more time alone," said Steffen Foerster from Duke University in US.
Researchers found that each chimpanzee carried roughly 20 to 25 per cent more bacterial species during the abundant and social wet season than during the dry season.
The microbiome differences were not solely due to seasonal changes in the fruit, leaves and insects that make up their diet, researchers found. The chimps' shifts between hobnobbing and loner lifestyles were also important.
"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," said Anne Pusey from Duke University.
The mix of bacteria in the animals' bowels was just as similar between unrelated individuals as it was between mothers and offspring, researchers found.
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 mothers.
The findings were published in the journal Science Advances.
