02 August 2023

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Penn Dental Medicine, UNC study identifies new bacterial species in tooth decay

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Streptococcus mutans has been implicated as the primary pathogen in childhood caries or tooth decay. While the role of polymicrobial communities is appreciated, it remains unclear whether other microorganisms are active contributors or interact with pathogens.

Researchers from Penn Dental Medicine and the University of North Carolina have now discovered that the bacterial species Selenomonas sputigena plays an important role in tooth decay, according to a news release.

In this study, researchers integrated multi-omics of supragingival biofilm (dental plaque) from 416 preschool-age children (208 males and 208 females) in a discovery-validation pipeline to identify disease-relevant inter-species interactions. Sixteen taxa associate with childhood caries in metagenomics-metatranscriptomics analyses.

The team examined biofilm formation dynamics, spatial arrangement, and metabolic activity of Selenomonas sputigena, Prevotella salivae and Leptotrichia wadei, either individually or with S. mutans. We show that S. sputigena, a flagellated anaerobe with previously unknown role in supragingival biofilm, becomes trapped in streptococcal exoglucans, loses motility but actively proliferates to build a honeycomb-like multicellular-superstructure encapsulating S. mutans, enhancing acidogenesis.

Rodent model experiments reveal an unrecognized ability of S. sputigena to colonize supragingival tooth surfaces. While incapable of causing caries on its own, when co-infected with S. mutans, S. sputigena causes extensive tooth enamel lesions and exacerbates disease severity in vivo.

In the news release, senior author Dr. Michel Koo from Penn Dental Medicine said the research provides new insights into the development of caries. The study "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," he said. 

The researchers now plan to study in more detail how this anaerobic motile bacterium ends up in the aerobic environment of the tooth surface. 

Koo is a 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.

Additional co-senior authors of the study were Drs. Kimon Divaris and Di Wu from the University of North Carolina.

Cho, H., Ren, Z., Divaris, K. et al. "Selenomonas sputigena acts as a pathobiont mediating spatial structure and biofilm virulence in early childhood caries." Nat Commun 14, 2919 (2023). https://doi.org/10.1038/s41467-023-38346-3.