Streptococcus salivarius promotes mucin putrefaction and malodor production by Porphyromonas gingivalis

Although the contribution of the oral microbiota to oral malodor is well-documented, the potential role of Gram-positive micro-organisms is unclear. In the current study, we tested the hypothesis that Gram-positive micro-organisms contribute to malodor production by deglycosylating oral glycoproteins, rendering them susceptible to subsequent proteolysis. To this end, we examined the effect of Streptococcus salivarius on Porphyromonas gingivalis-mediated putrefaction of a model glycoprotein (pig gastric mucin). Malodor was scored by two odor judges, and volatile sulfides were determined with the use of a sulfide monitor. Mucin degradation was followed by electrophoresis on SDS-PAGE. Results showed that the addition of S. salivarius or β-galactosidase promoted mucin degradation and concomitant malodor production. Addition of glycosidic inhibitors (p-APTG and glucose) inhibited this process. These results suggest that Gram-positive micro-organisms such as S. salivarius contribute to oral malodor production by deglycosylating salivary glycoproteins, thus exposing their protein core to further degradation by Gram-negative micro-organisms.