Systemic inactivation and phenotypic characterization of two-component systems in expression of Streptococcus mutans virulence properties

Aims: To assess potential function of each two-component signal transduction system in the expression of Streptococcus mutans virulence properties. Methods and Results: For each two-component system (TCS), the histidine kinase-encoding gene was inactivated by a polymerase chain reaction (PCR)-based deletion strategy and the effects of gene disruption on the cell's ability to form biofilms, become competent, and tolerate acid, osmotic, and oxidative stress conditions were tested. Our results demonstrated that none of the mutations were lethal for S. mutans. The TCS-2 (CiaRH) is involved in biofilm formation and tolerance to environmental stresses, the TCS-3 (ScnRK-like) participates in the survival of cells at acidic pH, and the TCS-9 affects the acid tolerance response and the process of streptococcal competence development. Conclusion: Our results confirmed the physiological role of the TCS in S. mutans cellular function, in particular the SncRK-like TCS and TCS-9 as they may represent new regulatory systems than can be involved in S. mutans pathogenesis. Significance and Impact of the study: Multiple TCS govern important biological parameters of S. mutans enabling its survival and persistence in the biofilm community.