Streptococcus A12 Modifies the Architecture of Streptococcus mutans Biofilms

Objectives: The overarching goal of this research is to understand how beneficial bacteria promote health-associated biofilms and prevent the emergence of pathogens. The specific goal of this project was to assess the effects of A12 on the formation of extracellular matrix by S. mutans.
Methods: Biofilms and planktonic cultures were established in defined medium or in supernates derived from A12 or S. mutans. The architecture of S. mutans biofilms was examined, exo-polysaccharide composition was compared, extracellular DNA (eDNA) was measured, glucan-mediated aggregation was assayed, GTF production was monitored by Western blotting, and qRT-PCR was used to measure expression of target genes.
Results: Compared to controls, the polysaccharide composition of S. mutans growing in A12 supernates was more water-soluble and cells produced less eDNA. A12 supernates did not affect GTF protein production, but preliminary qPCR experiments indicated that A12 supernates could alter expression of genes that contribute to pathogenesis, compared to controls.
Conclusions: In addition to already established mechanisms for inhibition of S. mutans by Streptococcus A12, A12 can alter the extracellular matrix of S. mutans in a way that compromises biofilm stability, which may reduce the cariogenic potential of S. mutans. This study contributes to the foundation of knowledge needed for the rational design of probiotics that can foster oral health.