title: Effect of an orphan response regulator on Streptococcus mutans sucrose-dependent adherence and cariogenesis.
abstract: Streptococcus mutans is the principal acidogenic component of dental plaque that demineralizes tooth enamel, leading to dental decay. Cell-associated glucosyltransferases catalyze the sucrose-dependent synthesis of sticky glucan polymers that, together with glucan binding proteins, promote S. mutans adherence to teeth and cell aggregation. We generated an S. mutans Tn916 transposon mutant, GMS315, which is defective in sucrose-dependent adherence and significantly less cariogenic than the UA130 wild-type progenitor in germfree rats. The results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis, Western blotting, and N-terminal sequence analysis confirmed the absence of a 155-kDa glucosyltransferase S (Gtf-S) from GMS315 protein profiles. Mapping of the unique transposon insertion in GMS315 revealed disruption of a putative regulatory region located upstream of gcrR, a gene previously described by Sato et al. that shares significant amino acid identity with other bacterial response regulators (Y. Sato, Y. Yamamoto, and H. Kizaki, FEMS Microbiol. Lett. 186: 187-191, 2000). The gcrR regulator, which we call "tarC," does not align with any of the 13 proposed two-component signal transduction systems derived from in silico analysis of the S. mutans genome, but rather represents one of several orphan response regulators in the genome. The results of Northern hybridization and/or real-time reverse transcription-PCR experiments reveal increased expression of both Gtf-S and glucan binding protein C (GbpC) in a tarC knockout mutant (GMS900), thereby supporting the notion that TarC acts as a negative transcriptional regulator. In addition, we noted that GMS900 has altered biofilm architecture relative to the wild type and is hypocariogenic in germfree rats. Taken collectively, these findings support a role for signal transduction in S. mutans sucrose-dependent adherence and aggregation and implicate TarC as a potential target for controlling S. mutans-induced cariogenesis.
authors.affiliation: Department of Biology, Middlebury College, Middlebury Vermont 05753, USA.
authors.forename: Vincent
authors.initials: V
authors.lastname: Idone
authors.forename: Stacy
authors.initials: S
authors.lastname: Brendtro
authors.forename: Robert
authors.initials: R
authors.lastname: Gillespie
authors.forename: Steve
authors.initials: S
authors.lastname: Kocaj
authors.forename: Erica
authors.initials: E
authors.lastname: Peterson
authors.forename: Mara
authors.initials: M
authors.lastname: Rendi
authors.forename: Wayne
authors.initials: W
authors.lastname: Warren
authors.forename: Suzanne
authors.initials: S
authors.lastname: Michalek
authors.forename: Kirsten
authors.initials: K
authors.lastname: Krastel
authors.forename: Dennis
authors.initials: D
authors.lastname: Cvitkovitch
authors.forename: Grace
authors.initials: G
authors.lastname: Spatafora
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001422:Bacterial Adhesion / Q000235:genetics / Q000502:physiology*; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology; D001483:Base Sequence; D018441:Biofilms; D004269:DNA, Bacterial / Q000235:genetics; D003731:Dental Caries / Q000209:etiology* / Q000382:microbiology; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D005856:Germ-Free Life; D005964:Glucosyltransferases / Q000235:genetics / Q000502:physiology; D006801:Humans; D008855:Microscopy, Electron, Scanning; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D051381:Rats; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D013295:Streptococcus mutans / Q000235:genetics / Q000472:pathogenicity* / Q000502:physiology*; D013395:Sucrose / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D013395:Sucrose; D005964:Glucosyltransferases