Collaborating researchers from Penn Dental Medicine and the University of North Carolina (UNC) have discovered that the bacterial species Selenomonas sputigena can have an important role in tooth decay.
Scientists have long considered another bacterial species, the plaque-forming, acid-making Streptococcus mutans, as the principal cause of tooth decay—also known as caries. However, in a study that appeared in Nature Communications, the researchers showed that S. sputigena, previously associated only with gum disease, can work as a key partner of S. mutans, greatly enhancing its cavity-making power.
“This gives new insights into the development of caries, highlights potential targets for prevention, and reveals novel mechanisms by which different species work together to form biofilms that may be relevant in other clinical contexts,” said co-senior author Dr. Michel Koo, professor in the Department of Orthodontics and Divisions of Pediatrics and Community Oral Health and Co-Director of the Center for Innovation & Precision Dentistry at Penn Dental Medicine.
The other co-senior authors of the study were Dr. Kimon Divaris and Dr. Di Wu of UNC.
Caries is considered the most common chronic disease worldwide. It arises when S. mutans and other acid-making bacteria build up on teeth and form plaque. Within plaque, these bacteria consume sugars from drinks or food, converting them to acids. If the plaque is left in place for too long, these acids start to erode the enamel, in time, creating cavities.
Scientists in past studies of plaque bacterial contents have identified a variety of other species in addition to S. mutans. These include species of Selenomonas, an “anaerobic,” non-oxygen-requiring group of bacteria more commonly found beneath the gum in cases of gum disease. This new study is the first to identify a cavity-causing role for a specific Selenomonas species.
The data showed that although S. sputigena is only one of several caries-linked bacterial species in plaque, and does not cause caries on its own, it has a striking ability to partner with S. mutans to boost the caries process. The result of this unexpected partnership, as the researchers showed using animal models, is a greatly increased and concentrated production of acid, which significantly worsens caries severity.
The researchers now plan to study in more detail how this anaerobic motile bacterium ends up in the aerobic environment of the tooth surface.
