Elusive Oral Bacteria Finally Isolated and Counted

Dentistry Today


Researchers at the University of Washington (UW) School of Dentistry and the Forsyth Institute have taken a significant step forward in the study of TM7, a group of microbes that may be linked to gum disease but are difficult to cultivate in the lab. 

After culturing TM7 for the first time in a test tube and sequencing its genome in 2015, UW and Forsyth researchers found that it is an ultra-small bacterial parasite with a tiny genome that lives and feeds on other bacteria, making it difficult to isolate and examine. 

Now, UW and Forsyth researchers have isolated TM7 bacteria from their host and counted them individually before adding the bacteria back to their host cultures. This allows the researchers to see how TM7 infects and parasitizes its hosts and uncover the mechanism it uses to establish a long-term parasitic relationship with those hosts.

The finding also may explain why TM7 bacteria persist for so long in the human mouth. The system that was used could be used to study other types of ultra-small bacteria as well, the researchers said.

“We are continuing to learn about how this TM7 species and other ultra-small bacteria like them are able to survive and find other cells to live on, since they are found in every human body and increase in number within certain oral diseases,” said Jeffrey McLean, PhD, MSc, associate professor of periodontics at the UW School of Dentistry.

The study, “Rapid Evolution of Decreased Host Susceptibility Drives a Stable Relationship Between Ultrasmall Parasite TM7x and Its Bacterial Host,” was published by the Proceedings of the National Academy of Sciences of the United States of America.

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