Modification of Gene Expression and Virulence Traits in Streptococcus mutans in Response to Carbohydrate Availability

Abstract

ABSTRACTThe genetic and phenotypic responses ofStreptococcus mutans, an organism that is strongly associated with the development of dental caries, to changes in carbohydrate availability were investigated.S. mutansUA159 or a derivative of UA159 lacking ManL, which is the EIIAB component (EIIABMan) of a glucose/mannose permease of the phosphoenolpyruvate:sugar phosphotransferase system (PTS) and a dominant effector of catabolite repression, was grown in continuous culture to steady state under conditions of excess (100 mM) or limiting (10 mM) glucose. Microarrays using RNA fromS. mutansUA159 revealed that 174 genes were differentially expressed in response to changes in carbohydrate availability (P< 0.001). Glucose-limited cells possessed higher PTS activity, could acidify the environment more rapidly and to a greater extent, and produced more ManL protein than cultures grown with excess glucose. Loss of ManL adversely affected carbohydrate transport and acid tolerance. Comparison of the histidine protein (HPr) inS. mutansUA159 and themanLdeletion strain indicated that the differences in the behaviors of the strains were not due to major differences in HPr pools or HPr phosphorylation status. Therefore, carbohydrate availability alone can dramatically influence the expression of physiologic and biochemical pathways that contribute directly to the virulence ofS. mutans, and ManL has a profound influence on this behavior.