From the perspective of A. Murat Eren, Ph.D., the mouth is the perfect place to study microbial communities. "Not only is it the beginning of the GI tract, but it's also 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 Eren, an assistant professor in the Department of Medicine at the University of Chicago.
source https://phys.org/news/2020-12-microbes-dental-plaque-relatives-soil.html
