title: A VicRK signal transduction system in Streptococcus mutans affects gtfBCD, gbpB, and ftf expression, biofilm formation, and genetic competence development.
abstract: Bacteria exposed to transient host environments can elicit adaptive responses by triggering the differential expression of genes via two-component signal transduction systems. This study describes the vicRK signal transduction system in Streptococcus mutans. A vicK (putative histidine kinase) deletion mutant (SmuvicK) was isolated. However, a vicR (putative response regulator) null mutation was apparently lethal, since the only transformants isolated after attempted mutagenesis overexpressed all three genes in the vicRKX operon (Smuvic+). Compared with the wild-type UA159 strain, both mutants formed aberrant biofilms. Moreover, the vicK mutant biofilm formed in sucrose-supplemented medium was easily detachable relative to that of the parent. The rate of total dextran formation by this mutant was remarkably reduced compared to the wild type, whereas it was increased in Smuvic+. Based on real-time PCR, Smuvic+ showed increased gtfBCD, gbpB, and ftf expression, while a recombinant VicR fusion protein was shown to bind the promoter regions of the gtfB, gtfC, and ftf genes. Also, transformation efficiency in the presence or absence of the S. mutans competence-stimulating peptide was altered for the vic mutants. In vivo studies conducted using SmuvicK in a specific-pathogen-free rat model resulted in significantly increased smooth-surface dental plaque (Pearson-Filon statistic [PF], <0.001). While the absence of vicK did not alter the incidence of caries, a significant reduction in SmuvicK CFU counts was observed in plaque samples relative to that of the parent (PF, <0.001). Taken together, these findings support involvement of the vicRK signal transduction system in regulating several important physiological processes in S. mutans.
authors.affiliation: Dental Research Institute, University of Toronto, 124 Edward Street, Toronto ON M51G6, Canada.
authors.forename: M Dilani
authors.initials: MD
authors.lastname: Senadheera
authors.forename: Bernard
authors.initials: B
authors.lastname: Guggenheim
authors.forename: Grace A
authors.initials: GA
authors.lastname: Spatafora
authors.forename: Yi-Chen Cathy
authors.initials: YC
authors.lastname: Huang
authors.forename: Jison
authors.initials: J
authors.lastname: Choi
authors.forename: David C I
authors.initials: DC
authors.lastname: Hung
authors.forename: Jennifer S
authors.initials: JS
authors.lastname: Treglown
authors.forename: Steven D
authors.initials: SD
authors.lastname: Goodman
authors.forename: Richard P
authors.initials: RP
authors.lastname: Ellen
authors.forename: Dennis G
authors.initials: DG
authors.lastname: Cvitkovitch
mesh_terms: D000818:Animals; D001422:Bacterial Adhesion / Q000502:physiology; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000502:physiology*; D018441:Biofilms / Q000254:growth & development; D002874:Chromosome Mapping; D002876:Chromosomes, Bacterial; D003731:Dental Caries / Q000382:microbiology; D015870:Gene Expression / Q000502:physiology*; D009154:Mutation; D051381:Rats; D015398:Signal Transduction / Q000502:physiology*; D013047:Specific Pathogen-Free Organisms; D013295:Streptococcus mutans / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D014169:Transformation, Bacterial / Q000235:genetics; D014774:Virulence / Q000235:genetics
chemical_list: D001426:Bacterial Proteins