By Sheena Faherty, biology Ph.D. candidate
Can the microorganisms living in a baby lemur’s gut help it grow up to be a vegetarian or an omnivore?
A new study appearing May 13 in Plos One shows that baby lemurs’ gut bacteria have different, diet-dependent strategies for reaching adult mixtures of microbes. This, in turn, might contribute to why some lemurs are strictly leaf-eaters, while some nosh on just about everything.
Erin McKenney, lead author on the study and a Ph.D. candidate in the Biology department, is looking at the patterns of how the bacteria colonize the gut of their lemur host and why this is essential for helping the adult lemurs navigate their environment — and their diets.
“This study is important because all mammals are born with basically sterile guts,” McKenney said. “But by the time we’re adult mammals, there are 20 trillion bacteria living in the gut. (The bugs are an) adaptive super organ that has co-evolved with the host and dictated the host’s evolution. We want to know more about how that happens.”
This “microbiome” of the gut is a jack-of-all-trades, performing jobs like protecting the host’s body from pathogens and helping it digest food. When the gut’s microbes digest foods that are high in fiber — like plant matter — some of the digestion by-products are absorbed by the intestine, which provides nutrition for the body. Humans get up to 10 percent of our daily nutritional requirements from fiber breakdown by bacteria.
“Mammals don’t secrete the enzymes that are necessary, so no mammal can digest fiber on its own,” McKenney said. “These microbes are performing an incredibly important life process for us.”
At the Duke Lemur Center, McKenney collected fecal samples from three different species of lemur that evolved to eat different foods—a strict leaf-eater, and two omnivores. Using DNA sequencing, she determined the communities of bacteria that are living in their guts at different life stages from birth to adulthood.
Watching microbiomes through time may enable her to answer the question of how the microbiome of each species becomes teeming with 20 trillion bacteria, and if the patterns differ based on diet.
The results suggest that all species of baby lemurs, when they are born and nursing from their mothers have similar microbiome profiles that are much less complex than adult profiles. But leaf-eaters that eat the most fiber show adult microbiome profiles as soon as solid foods are introduced, which is in contrast to the other two species that take longer to reach adult microbiome profiles. Additionally, leaf-eaters have more complex microbial communities, which allows them to digest fiber-rich foods.
“So when you start to think about the really big picture, beyond everything the gut microbes do for the hosts they live inside of, we find the microbes have done an incredible service to mammalian speciation. The only way that we have leaf-eaters is because of these gut microbes,” McKenney said.