MICROBES in the mouth fascinates A. Murat Eren, doctor of Philosophy (Ph.D.).
“It’s a very special and small environment that’s microbially diverse enough that we can really start to answer interesting questions about microbiomes and their evolution,” said Dr. Eren, an assistant professor in the Department of Medicine at the University of Chicago (UChicago).
“There’s a surprising amount of site-specificity, in that you find defined patterns of microbes in different areas of the mouth – the microbes associated with the tongue are very different from those on the plaque on your teeth,” he pointed out.
“Your tongue microbes are more similar to those living on someone else’s tongue than they are to those living in your throat or on your gums!”
The unique ecology is the subject of a new study published in December in Genome Biology. The study was conducted by Dr. Eren and a team of researchers at UChicago and the Marine Biological Laboratory, Woods Hole.
They used state-of-the-art analysis to look closer at the mouth microbiome or micro-environment.
Then they zoomed in on Saccharibacteria (TM7), a bacteria particularly difficult to study, according to the UChicago website.
“Normally, when we study a microbial environment, we take samples and only read a small fraction of the genomes present – just enough to ID the broad categories of microbes,” explained Dr. Eren.
They found that different TM7 species could be grouped separately based on the similarities of their genomes which indicate how recently the different species split from one another in their evolutionary history.
The research team was surprised to find that the TM7 species from dental plaque grouped more closely with the TM7 species found in dirt. The TM7 species on the tongue grouped more closely with species found in the gastrointestinal tract.
The first time he realized they were completely separate, “my mind exploded,” said Alon Shaiber, Ph.D., the study’s first author and now a genomics data scientist at Weill Cornell Medicine. “We did not expect that at all.”
A UChicago news release said the findings hint at how microbes might make the transition from the environment into the human body.
“Our hypothesis is that plaque played a role during the evolution of host-associated microbes, such as some clades of TM7, by offering this intermediary space where the bacteria don’t immediately have to deal with threats from the host,” said Dr. Eren.
“Once adapted to the plaque, the microbes could then make the jump to adapt to the host entirely, in new habitats like the tongue,” he added. “This was the most exciting thing to us. This showed that the dental plaque, the enemy of our health that we constantly try to get rid of, may at some point have played an important role in the evolution of some of the microbes to call our bodies their home.”
It means the researchers could identify new species of bacteria from the oral cavity that had not previously been studied because cultivating some of these microbes in the laboratory is difficult.
“The mouth is so easily accessible that people have been working on bacteria from the mouth for a long time,” said Jessica Mark Welch, Ph.D., the study’s co-senior author, and an Associate Scientist at the Marine Biological Laboratory. “But we’re finding that there are entire new microbial groups, including a few really weird and unusual ones, that have not been looked at before.”
The study provides new insights on the role of oral microbes in human health./PN
