Open AccessThe two‐component system sivS/R regulates virulence in Streptococcus iniae
Author(s) -
Bolotin Shelly,
Fuller Jeffrey D.,
Bast Darrin J.,
de Azavedo Joyce C.S.
Publication year - 2007
Publication title -
fems immunology & medical microbiology
Language(s) - English
Resource type - Journals
eISSN - 1574-695X
pISSN - 0928-8244
DOI - 10.1111/j.1574-695x.2007.00334.x
Subject(s) - streptococcus iniae , biology , virulence , microbiology and biotechnology , mutant , plasmid , streptolysin , gene , genetics , bacterial protein
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 9117Δ siv , 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 .