title: The two-component system sivS/R regulates virulence in Streptococcus iniae.
abstract: Streptococcus iniae causes invasive disease and death in fish, and to a lesser extent, sporadic cases of soft-tissue infections in humans. A two-component system termed sivS/R, which regulates capsule expression, was previously identified and characterized. In this study, it is shown that a sivS/R deletion-insertion mutant, termed 9117Deltasiv, causes transient bacteremia and reduced virulence compared with the parent strain when tested in a murine model of bacteremic infection. Furthermore, real-time PCR studies indicated that SivS/R regulates the expression levels of the streptolysin S structural gene, sagA, as well as the CAMP factor gene, cfi. Sodium dodecyl sulphate polyacrylamide gel electrophoresis of S. iniae spheroplasts revealed downregulation of three surface proteins in the mutant strain compared with the parent strain. These proteins were identified by MS to be a putative lipoprotein, a hyaluronate-associated protein and a pyruvate kinase. This study demonstrates that SivS/R regulates virulence in vivo, and controls the expression of a number of genes in S. iniae.
authors.affiliation: Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada.
authors.forename: Shelly
authors.initials: S
authors.lastname: Bolotin
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Fuller
authors.forename: Darrin J
authors.initials: DJ
authors.lastname: Bast
authors.forename: Joyce C S
authors.initials: JC
authors.lastname: de Azavedo
mesh_terms: D000818:Animals; D016470:Bacteremia; D001426:Bacterial Proteins / Q000032:analysis / Q000096:biosynthesis / Q000235:genetics / Q000302:isolation & purification; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D006460:Hemolysin Proteins / Q000096:biosynthesis / Q000235:genetics; D013058:Mass Spectrometry; D008565:Membrane Proteins / Q000032:analysis / Q000302:isolation & purification; D051379:Mice; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D012329:RNA, Bacterial / Q000096:biosynthesis; D012333:RNA, Messenger / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D015398:Signal Transduction; D013291:Streptococcus / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D013301:Streptolysins / Q000096:biosynthesis / Q000235:genetics; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; C039092:CAMP protein, Streptococcus; D004269:DNA, Bacterial; D006460:Hemolysin Proteins; D008565:Membrane Proteins; D012329:RNA, Bacterial; D012333:RNA, Messenger; D013301:Streptolysins; C026050:streptolysin S