(245a) Salivary Mucin Glycans Suppress Quorum Sensing and Associated Virulence Traits in Streptococcus Mutans

Mucus barriers accommodate hundreds of trillions of microbes throughout the human body, while preventing pathogenic colonization. In the oral cavity for instance, saliva containing the salivary mucins MUC5B and MUC7 forms a slippery mucosal pellicle that coats the soft tissue and teeth to prevent infection by oral pathogens. Previous studies have found salivary mucins can interact directly with microbes through selective agglutinin activity and bacterial binding, but the extent of saliva’s protective functions and their underlying mechanisms are not well understood. Here, we identify that native saliva, and specifically, its gel-forming mucin polymer MUC5B, dramatically inhibits infection-related traits in a clinically-important oral pathogen, Streptococcus mutans. In particular, we find MUC5B overrides bacterial communication by suppressing key quorum sensing pathways regulated by the Competence Stimulating Peptide (CSP) and the SigX Inducing Peptide (XIP). These quorum sensing signaling systems regulate the expression of virulence factors that enable infection of the host. We show that MUC5B suppresses two of these problematic traits, namely, bacteriocin production and the acquisition of competence, a prerequisite for natural genetic transformation. Our data reveal that MUC5B's suppression of quorum sensing is mediated by mucin glycans. We find that these glycans are highly effective at suppressing quorum sensing and the acquisition of competence even when removed from the mucin backbone. Together, these results suggest that mucin-type glycans represent highly attractive compounds for the prevention of S. mutans virulence in the oral cavity.