title: Bidirectional signaling in the competence regulatory pathway of Streptococcus mutans.
abstract: Streptococcus mutans expresses comX (also known as sigX), which encodes a sigma factor that is required for development of genetic competence, in response to the peptide signals XIP and CSP and environmental factors. XIP (sigX inducing peptide) is derived from ComS and activates comX unimodally in chemically defined media via the ComRS system. CSP (competence stimulating peptide) activates comX bimodally in peptide-rich media through the ComDE two-component system. However, CSP-ComDE activation of comX is indirect and involves ComRS. Therefore, the bimodality of CSP-dependent activation of comX may arise from either ComRS or ComDE. Here we study, at the single-cell level, how genes in the CSP signaling pathway respond to CSP, XIP and media. Our data indicate that activation of comX stimulates expression of comE. In addition, activation of comE requires intact comR and comS genes. Therefore, not only does CSP-ComDE stimulate the ComRS pathway to activate comX expression, but ComRS activation of comX also stimulates expression of the CSP-ComDE pathway and its regulon. The results demonstrate the mutual interconnection of the signaling pathways that control bacteriocin expression (ComDE) and genetic competence (ComRS), both of which are linked to lytic and virulence behaviors.
authors.affiliation: Department of Physics, University of Florida, Gainesville FL 32611, USA.
authors.forename: Minjun
authors.initials: M
authors.lastname: Son
authors.affiliation: Department of Oral Biology, College of Dentistry, University of Florida, Gainesville, Florida 32610, USA.
authors.forename: Robert C
authors.initials: RC
authors.lastname: Shields
authors.affiliation: Department of Oral Biology, College of Dentistry, University of Florida, Gainesville, Florida 32610, USA.
authors.forename: Sang-Joon
authors.initials: SJ
authors.lastname: Ahn
authors.affiliation: Department of Oral Biology, College of Dentistry, University of Florida, Gainesville, Florida 32610, USA.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Burne
authors.affiliation: Department of Physics, University of Florida, Gainesville FL 32611, USA sjhagen@ufl.edu.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Hagen
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001430:Bacteriocins / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D053038:Quorum Sensing; D012808:Sigma Factor / Q000235:genetics; D015398:Signal Transduction / Q000235:genetics*; D059010:Single-Cell Analysis; D013295:Streptococcus mutans / Q000235:genetics* / Q000378:metabolism* / Q000472:pathogenicity; D014157:Transcription Factors / Q000235:genetics; D014774:Virulence / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D001430:Bacteriocins; C061262:ComA protein, Bacteria; C120829:ComX protein, Streptococcus; D004268:DNA-Binding Proteins; D012808:Sigma Factor; D014157:Transcription Factors; C423628:competence factor, Streptococcus
keywords: bimodality; bistability; feedback; fluorescence; quorum sensing; single cell; transformation