Inside the guts of every vertebrate, including humans, are a community of microbes—including bacteria, viruses, and fungi—known as the microbiome. Parts of the microbiome help our bodies to perform essential functions related to nutrition and immunity, and their compositions are unique to their hosts. But scientists are still trying to figure out how the microbiome might have influenced the evolution of animal life on Earth.
“It’s not feasible to sample the microbiomes of all mammal species, but bats, which make up about 20 percent of all living mammals, can serve as an ideal model organism,” says Melissa Ingala, a doctoral candidate in the Museum’s Richard Gilder Graduate School and lead author of a review published today in the journal mSphere that proposes studying the microbiome of bats holds great potential.
There are nearly 1,400 described bat species around the world, occupying every continent except Antarctica. In addition to their global distribution and large numbers, bats also stand out among mammals because of their dietary diversity, with food preferences that include fruits, insects, meat, nectar, and even blood.
In mammals, it can be challenging to distinguish between the ways in which diet and evolutionary relationships affect microbiome evolution because many groups of closely related mammals share the same diet. Among bats, however, several feeding modes evolved in parallel two or more times, allowing researchers to study bat microbiomes across a range of diets and tease apart the variables.
Bats and their microbes are increasingly recognized as important components of zoonotic disease cycles, and have been known or suspected to be the reservoir of several viruses that are lethal to humans, including SARS, Ebola, and rabies. Studying bat microbiomes has the potential to directly inform human health and could help explain the epidemiology of these emerging infectious diseases.
“In addition to their role in emerging infectious diseases among wildlife and humans, understanding the microbiomes of bats can also teach us more about bats’ ability to carry out vital and economically important ecosystem functions like insect pest control and pollination,” says Ingala.
Bats may also be used to investigate the links between the microbiome and the evolution of other natural processes, such as immunity and aging.
Recent studies in lab animals—primarily mice—have found direct links between the microbiome and the lifespan of the host. But the common strain of mice used in these studies has a lifespan of about a year and a half. Bats can live much longer—about 40 years—making them a better model for humans. Many bats also return to the same roosts year after year, making it possible for researchers to sample the same animal’s microbiome throughout its lifetime.
“Bats really represent an untapped resource for understanding microbiome evolution in mammals,” Ingala says. “In recent years, we have heard a great deal about the human microbiome and its potential transformation on medicine. It’s time for wildlife microbiome research to catch up.”