title: Rga is a regulator of adherence and pilus formation in Streptococcus agalactiae.
abstract: Streptococcus agalactiae is the leading cause of bacterial sepsis and meningitis in neonates and is also the causative agent of several serious infections in immunocompromised adults. S. agalactiae encounters multiple niches during an infection, suggesting that regulatory mechanisms control the expression of specific virulence factors in this bacterium. The present study describes the functional characterization of a gene from S. agalactiae, designated rga, which encodes a protein with significant similarity to members of the RofA-like protein (RALP) family of transcriptional regulators. After deletion of the rga gene in the genome of S. agalactiae, the mutant strain exhibited significantly reduced expression of the genes srr-1 and pilA, which encode a serine-rich repeat surface glycoprotein and a pilus protein, respectively, and moderately increased expression of the fbsA gene, which encodes a fibrinogen-binding protein. Electrophoretic mobility shift assays demonstrated specific DNA binding of purified Rga to the promoter regions of pilA and fbsA, suggesting that Rga directly controls pilA and fbsA. Adherence assays revealed significantly reduced binding of the Δrga mutant to epithelial HEp-2 cells and to immobilized human keratin 4, respectively. In contrast, the adherence of the Δrga mutant to A549 cells and its binding to human fibrinogen was significantly increased. Immunoblot and immunoelectron microscopy revealed that the quantity of pilus structures was significantly reduced in the Δrga mutant compared with the parental strain. The wild-type phenotype could be restored by plasmid-mediated expression of rga, demonstrating that the mutant phenotypes resulted from a loss of Rga function.
authors.affiliation: Institute of Microbiology and Biotechnology, University of Ulm, 89069 Ulm, Germany.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Samen
authors.affiliation: Institute of Microbiology and Biotechnology, University of Ulm, 89069 Ulm, Germany.
authors.forename: Beate
authors.initials: B
authors.lastname: Heinz
authors.affiliation: Institute of Microbiology and Biotechnology, University of Ulm, 89069 Ulm, Germany.
authors.forename: Heike
authors.initials: H
authors.lastname: Boisvert
authors.affiliation: Institute of Microbiology and Biotechnology, University of Ulm, 89069 Ulm, Germany.
authors.forename: Bernhard J
authors.initials: BJ
authors.lastname: Eikmanns
authors.affiliation: University of Applied Sciences Bonn-Rhein-Sieg, 53359 Rheinbach, Germany.|Institute of Microbiology and Biotechnology, University of Ulm, 89069 Ulm, Germany.
authors.forename: Dieter J
authors.initials: DJ
authors.lastname: Reinscheid
authors.affiliation: Laboratoire d'Ingénierie des Biomolécules, Nancy Université, ENSAIA - INPL, 54505 Vandoeuvre-lès-Nancy, France.|Institute of Microbiology and Biotechnology, University of Ulm, 89069 Ulm, Germany.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Borges
mesh_terms: D018829:Adhesins, Bacterial / Q000096:biosynthesis*; D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D004269:DNA, Bacterial / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D004847:Epithelial Cells / Q000382:microbiology; D010861:Fimbriae, Bacterial / Q000502:physiology*; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D007633:Keratins / Q000378:metabolism; D011485:Protein Binding; D013292:Streptococcus agalactiae / Q000235:genetics / Q000472:pathogenicity*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D037521:Virulence Factors / Q000096:biosynthesis
chemical_list: D018829:Adhesins, Bacterial; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D014157:Transcription Factors; D037521:Virulence Factors; D007633:Keratins