Researchers Study New Contributor to Tooth Decay

Tooth decay can cause pain, infection and tooth loss. Bacteria that convert sugar to acid—and that can thrive in an acidic environment—are a major driver of tooth decay. 

An NIH-funded research team identified oral bacteria species found in the mouths of more than 400 children. Their study appeared in Nature Communications.

Using DNA and RNA sequencing of the microbial communities, the team found that 16 species of bacteria were more abundant among children with cavities. Using various techniques to study biofilms—communities of microbes that live together in a protective, sticky matrix—the investigators then teased out how these oral bacteria might cause cavities.

Based on their initial findings, the researchers selected four species for further study, including Streptococcus mutans, which was already known to be a major driver of tooth decay. The roles in tooth decay of the other three potential culprits hadn’t been explored. These were S. sputigena, Prevotella salivae and Leptotrichia wadei.

All four bacterial species could produce acid from sugar and survive in an acidic environment. The combination of S. mutans and S. sputigena produced the most acid, at higher rates than either species alone. This suggested they may have a cooperative relationship.

S. sputigena have appendages called flagella that normally let them move freely. But when grown with S. mutans, S. sputigena gets trapped in place by sticky compounds produced by S. mutans and form a honeycomb-like structure around clusters of S. mutans.

The structure created by the trapped S. sputigena provides a scaffold for further biofilm growth and acid production. When the researchers prevented S. mutans from producing the compound that traps S. sputigena, the bacterial duo could no longer produce biofilms or tooth-damaging acid.

Further research showed S. sputigena and S. mutans together caused substantially more tooth decay than S. mutans alone. This suggests that disrupting the interaction between these two bacteria may be a way to prevent cavities.—adapted from NIH Research Matters