A group of scientists gathered last week in the Forsyth Institute’s microbiology lab. But instead of running experiments, they were providing dental plaque samples.
Forsyth’s inaugural symposium, titled “the Uncultivable Bacteria,” convened researchers from all over the world to discuss a persistent challenge. Scientists want to understand the role of bacteria in the environments they inhabit, including the human body. To do that, researchers must be able to grow and study each type of bacteria in the lab.
So far, researchers have successfully cultivated about 65 percent of the 700 different types of known bacteria in the mouth. The other 35 percent has remained elusive. The only exception is a type called human oral Saccharibacteria, or TM7, which was grown for the first time in 2014 by researchers at Forsyth.
As part of the symposium, Forsyth scientists demonstrated how to grow TM7 using dental plaque samples from 12 of the conference participants. Researchers believe the same strategy used to cultivate TM7 could be applied to other previously uncultivable bacteria.
“Something out there is going to behave like TM7,” said Andrew Collins, a postdoctoral fellow in microbiology at Forsyth, who led the demonstration. “If we can grow those microbes in the lab too, it will open up another branch of bacteriology to study.”
Bugs in the mouth, bugs in the gut
Over the last few years, scientists have been investigating gut bacteria and their impact on human health. This community of microbes is complex, and we still know relatively little about them. Researchers also believe that bacteria in the mouth—known as the oral microbiome—is an entirely separate community from that in the gut.
“Whether they are talking to each other or not, that’s a different story,” said Pallavi Murugkar, a postdoctoral fellow in microbiology at Forsyth.
The bacteria in the mouth are different from the bacteria in the gut because microbes evolve to thrive in a certain type of environment. The gut and mouth environments are distinctive, with very different surfaces on which bacteria can attach.
“You can’t swap a polar bear with a panda bear and expect to have good results,” Collins said.
However, a variation of the bacteria TM7 exists in both the mouth and the gut, Collins explained. “Bears are in both bamboo forests and the arctic. They’re just different bears.”
The fact that TM7 exists in more than one type of environment suggests to scientists that understanding the human oral microbiome could also shed light on the gut microbiome, and other types of environments where bacteria play an important role.
Replicating the mouth
Researchers know the human microbiome is important for health, and that some bacteria are beneficial while others are harmful. But to get a complete picture of how microbes interact with one another to impact health, we need to replicate and study the entire microbial community.
For example, Pallavi explained that TM7s are parasitic, meaning they harm or kill their host bacteria. That sounds bad, but there could be more to the story.
“Are TM7s responsible for maintaining numbers of the bad bacteria, keeping them in check? If so, can they be used as a potential therapy method?” Pallavi said.
The only way to know the role of each microbe in the mouth is to grow them all and study their behavior and interactions. For example, “If we give that environment sugar, how does it lead to cavities or gum disease?” Pallavi said.
Forsyth’s recent symposium, which was attended by about 90 people, provided an opportunity for researchers to share their work in cultivating bacteria, with the ultimate goal of replicating microbial communities.
“I think the symposium will encourage many investigators to try the methods developed at Forsyth to culture other species of bacteria,” said Floyd Dewhirst, director of a microbiology lab at Forsyth. “One measure of a meeting’s success is whether it led to investigators initiating new collaborations. I’m happy to report that multiple collaborative projects were established during the two-day symposium.”
“We want to answer the bigger picture question—why are the bacteria there?” Pallavi said. “The more people around the world that are working on this, the faster we’ll get those answers.”