Closely-related bats may have completely different communities of microbes, according to a study which suggests that gut bacteria may not be as important for the flying furry mammals as it is for other animals.
Earlier studies have established that in several mammals, including humans, gut bacteria, help in digesting food and maintaining healthy immune systems, and researchers are still learning about the relationship between microbes and skin, gut, and oral health in other animals. But a study, published in the journal Systems, revealed that bats have fewer bacterial species living in their guts than in their mouths and on their skin -- suggesting that the flying rodents may not be as dependent on gut bacteria compared to other mammals.
The researchers, including those from Chicago's Field Museum in the US, took samples of bacteria from the skin, tongues, and guts of 497 bats from 31 different species in Kenya and Uganda, and compared the genetic code of the microbes.
They found that the kinds of bacteria living in the bats' guts varied from species to species without any apparent evolutionary pattern. According to the researchers, this was strange since for most other mammals, they said, closely-related hosts, share more similar microbiomes -- a pattern called phylosymbiosis.
"We conclude that the gut, oral, and skin microbiota of bats are shaped predominantly by ecological factors and do not exhibit the same degree of phylosymbiosis observed in other mammals," the researchers wrote in the study.
Holly Lutz, the study co-author from the Field Museum, said there's essentially no relationship between the bat microbiome and bat evolutionary history She said, usually one might expect to see similar microbiomes in closely-related species if animals strongly depended on their bacteria for survival.
"This is largely what we've seen in other mammals that have been studied, but it's just not there in bats," Lutz said animals require microbes for digestion and nutrient acquisition, which is true for humans but may not be true for all species.
"The trends we're seeing suggest that bats may not depend on bacteria the same way many other mammals do, and that they can survive just fine without a strict suite of bacteria in their guts to help them digest their food," she said. The species of a bat is still an important factor in predicting the microbiome, the researchers said. But this may be tied to where those bats live and what they eat, they added.
According to the study, the bat microbiome may be the result of bacteria that the bats pick up from their environment, as opposed to co-evolving with a specific ecosystem of microbes which is seen in other animals. "The same species of bat in five locations might host five very different microbial communities," Lutz said.
Since the gut bacteria of bats are more closely tied to where they live than where the species falls on the bat family tree, the researchers suggest that evolving a special relationship with the right kind of gut bacteria may not have been as important for the flying mammals as it has been for other animals.
According to Lutz, the unique relationships bats have with gut bacteria may be related to another trait that sets them apart from their fellow mammals -- their ability to fly. "Bats have extremely shortened guts," she said.
The study noted that food takes only fifteen to thirty minutes to pass through a bat's digestive system -- a third the time it takes for a similarly-sized rodent. This, the researchers speculated, is because a long, winding digestive tract may weigh the bats down, and affect their flight.
"For bats, you can't be carrying around non-essentials. You need to reduce weight for flying--you don't want a heavy gut," Lutz said. The study also noted that the gut bacteria ecosystem in bats resemble those of birds more than what is seen in mammals. The researchers cautioned that due to weaker dependence on gut microbes, bats may be impacted more severely by environmental changes.
"Bats may be very susceptible to environmental change -- if they have a transient microbiome, they might not have the most stable defense mechanisms. Human-caused disturbances to the environment are a very important issue. Bats may be extra-fragile and more at risk," Lutz said.