Different Roles of EIIAB Man and EII Glc in Regulation of Energy Metabolism, Biofilm Development, and Competence in Streptococcus mutans

Abstract

ABSTRACT The phosphoenolpyruvate:sugar phosphotransferase system (PTS) is the major carbohydrate transport system in oral streptococci. The mannose-PTS of Streptococcus mutans , which transports mannose and glucose, is involved in carbon catabolite repression (CCR) and regulates the expression of known virulence genes. In this study, we investigated the role of EII Glc and EIIAB Man in sugar metabolism, gene regulation, biofilm formation, and competence. The results demonstrate that the inactivation of ptsG , encoding a putative EII Glc , did not lead to major changes in sugar metabolism or affect the phenotypes of interest. However, the loss of EII Glc was shown to have a significant impact on the proteome and to affect the expression of a known virulence factor, fructan hydrolase ( fruA ). JAM1, a mutant strain lacking EIIAB Man , had an impaired capacity to form biofilms in the presence of glucose and displayed a decreased ability to be transformed with exogenous DNA. Also, the lactose- and cellobiose-PTSs were positively and negatively regulated by EIIAB Man , respectively. Microarrays were used to investigate the profound phenotypic changes displayed by JAM1, revealing that EIIAB Man of S. mutans has a key regulatory role in energy metabolism, possibly by sensing the energy levels of the cells or the carbohydrate availability and, in response, regulating the activity of transcription factors and carbohydrate transporters.