title: A novel role for SarX in Staphylococcus epidermidis biofilm regulation.
abstract: Biofilm production by staphylococci is an important virulence determinant mediated by the icaADBC-encoded polysaccharide intercellular adhesin (PIA) or by surface and extracellular proteins. Deletion of the Staphylococcus accessory regulator sarX significantly reduced biofilm-forming capacity in Staphylococcus epidermidis CSF41498, whereas multicopy sarX complemented the sarX mutant and increased wild-type biofilm production. In Staphylococcus aureus, SarX negatively regulates the accessory gene regulator (Agr) system, which in turn has strain-specific effects on biofilm regulation. Here we found that purified S. epidermidis SarX protein bound specifically to the agr P3 promoter. However RT-PCR analysis revealed that both mutation of sarX and multicopy sarX activated RNAIII transcription, making it difficult to correlate sarX-mediated biofilm regulation with altered agr activity. In contrast, RT-PCR and immunoblot analysis revealed that icaA transcription and PIA expression were decreased in the sarX mutant, whereas multicopy sarX increased ica and PIA expression. Furthermore, multicopy sarX did not promote biofilms in an icaC mutant. Finally, purified SarX protein bound specifically to the ica operon promoter. Taken together, these data reveal that the S. epidermidis SarX protein regulates the transcriptional activity of the agr and ica loci and controls the biofilm phenotype, primarily by regulating icaADBC transcription and PIA production.
authors.affiliation: School of Biomolecular and Biomedical Science and Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Rowe
authors.affiliation: Department of Clinical Microbiology, St James's Hospital, Trinity College, Dublin 8, Ireland.
authors.forename: Vivienne
authors.initials: V
authors.lastname: Mahon
authors.affiliation: Department of Clinical Microbiology, St James's Hospital, Trinity College, Dublin 8, Ireland.
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Smith
authors.affiliation: School of Biomolecular and Biomedical Science and Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: James P
authors.initials: JP
authors.lastname: O'Gara
mesh_terms: D001426:Bacterial Proteins / Q000302:isolation & purification / Q000378:metabolism*; D018441:Biofilms / Q000254:growth & development*; D004269:DNA, Bacterial / Q000378:metabolism; D017353:Gene Deletion; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D005816:Genetic Complementation Test; D015151:Immunoblotting; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012329:RNA, Bacterial / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013212:Staphylococcus epidermidis / Q000502:physiology*; D014157:Transcription Factors / Q000302:isolation & purification / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D011135:Polysaccharides, Bacterial; D012329:RNA, Bacterial; C096035:RNAIII, Staphylococcus aureus; D014157:Transcription Factors; C113579:polysaccharide intercellular adhesin