title: Environmental influences on competitive hydrogen peroxide production in Streptococcus gordonii.
abstract: Streptococcus gordonii is an important member of the oral biofilm. One of its phenotypic traits is the production of hydrogen peroxide (H2O2). H2O2 is an antimicrobial component produced by S. gordonii that is able to antagonize the growth of cariogenic Streptococcus mutans. Strategies that modulate H2O2 production in the oral cavity may be useful as a simple therapeutic mechanism to improve oral health, but little is known about the regulation of H2O2 production. The enzyme responsible for H2O2 production is pyruvate oxidase, encoded by spxB. The functional studies of spxB expression and SpxB abundance presented in this report demonstrate a strong dependence on environmental oxygen tension and carbohydrate availability. Carbon catabolite repression (CCR) modulates spxB expression carbohydrate dependently. Catabolite control protein A (CcpA) represses spxB expression by direct binding to the spxB promoter, as shown by electrophoretic mobility shift assays (EMSA). Promoter mutation studies revealed the requirement of two catabolite-responsive elements (CRE) for CcpA-dependent spxB regulation, as evaluated by spxB expression and phenotypic H2O2 production assays. Thus, molecular mechanisms for the control of S. gordonii spxB expression are presented for the first time, demonstrating the possibility of manipulating H2O2 production for increased competitive fitness.
authors.affiliation: Department of Microbiology and Parasitology, China Medical University, Shenyang City, Liaoning Province, People's Republic of China 110001. lyzheng@mail.cmu.edu.cn
authors.forename: Lanyan
authors.initials: L
authors.lastname: Zheng
authors.forename: Andreas
authors.initials: A
authors.lastname: Itzek
authors.forename: Zhiyun
authors.initials: Z
authors.lastname: Chen
authors.forename: Jens
authors.initials: J
authors.lastname: Kreth
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism; D050260:Carbohydrate Metabolism; D057465:Catabolite Repression; D004269:DNA, Bacterial / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D006861:Hydrogen Peroxide / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D011771:Pyruvate Oxidase / Q000378:metabolism*; D012097:Repressor Proteins / Q000378:metabolism; D054773:Streptococcus gordonii / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D012097:Repressor Proteins; C069286:catabolite control proteins, bacteria; D006861:Hydrogen Peroxide; D011771:Pyruvate Oxidase; D010100:Oxygen