The oral microbiome, which is collectively known as microbes in our mouths, has many effects on our overall health that we are still not fully understanding. Periodontitis can be caused by bacteria, which can also lead to other systemic diseases like diabetes and heart disease. Other oral organisms have been linked with certain types of carcinoma. Scientists are studying how these microbes interact with our bodies and other organisms to determine their individual roles in disease and health.
A Candidate Phyla Radiation (CPR) is one of many bacterial species that live in our mouths. These bugs are particularly mysterious because they are extremely small and live in a unique symbiotic relationship with their host bacteria. Dr. Xuesong He, a Forsyth Institute researcher, has cultivated TM7 bacteria for the first time in the CPR.
Dr. Dr. Jeffrey S. McLean, his collaborator at the University of Washington has developed a new model system that uses the first human oral TM7 strain, TM7x and its host bacterium. Actinomyces odontolyticus. The model system was used by researchers to experiment with these tiny bacteria. They tested a hypothesis about how TM7 adapts to living inside humans and provided empirical data to support previous genomic studies. Their findings were published today by the journal Proceedings of the National Academy of Sciences
Scientists have discovered TM7 in soil, groundwater, and other mammals. Studies have shown that while they share a similar genome, the TM7 in humans is different from others because they have a gene cluster encoding ADS.
This was interesting to us because there are very few genomic modifications that have occurred in this group, which is tiny bacteria with small genomes.
University of Washington, Dr. Jeffrey S. McLean
Researchers speculated that TM7 acquired ADS to aid them in adapting and surviving in the human oral cavity. Dr. Jing Tian (first author of the study) used the model system as a laboratory to test the hypothesis. ADS helped TM7x to break down arginine. This process produces the compounds Adenosinetriphosphate (ATP), as well as ammonia. TM7x’s infectivity, or ability of to multiply, was boosted by the increased levels of ATP/ammonia. It also protected TM7x from acid stress, a condition that microbes commonly encounter in the human mouth cavity as a result of the acid made when bacteria metabolize dietary carbohydrate.
The experiment revealed that TM7x could survive in the experimental environment longer than they could without ADS.
“Most current studies of CPR bacteria are based upon a culture-independent genetic approach. Dr. He.
Dr. Tian is a visiting scholar at Forsyth and a Pediatric Dentist at Peking University Hospital. Dr. Tian previously found that children with dental caries had a significantly higher abundance of TM7 after they were treated. Dr. Tian stated, “This suggests that TM7 may be more linked with a caries-free status, and we are planning more research in this field.”
This study also confirms that TM7 bacteria may play a stronger protective role in oral health than initially thought. Scientists believe that TM7 bacteria is responsible for periodontal disease. For example, TM7 levels are found to be high in patients with periodontal disease. A recent study led by Dr. Batbileg Bor of Forsyth found the opposite effect: TM7 reduced periodontal inflammation, and bone loss in a mouse model.
Dr. McLean stated that “we are still in the early stages understanding how each one of the many types of ultrasmall parasitic bacteria, that we basically just discovered within humans, is impacting health and diseases.”
Dr. He said. “Now, we have a manipulatable system for TM7 which is truly a significant advantage.”
