Brown RN, Gulig PA
Roles of RseB, {sigma}E, and DegP in virulence and phase variation of colony morphotype of Vibrio vulnificus. [JOURNAL ARTICLE]
Infect Immun 2009 Jun 29.
Vibrio vulnificus is an estuarine bacterium capable of causing serious and often fatal wound infection and primary septicemia. We used alkaline phosphatase insertion mutagenesis to identify genes necessary for virulence of this pathogen. One mutant had an in-frame fusion of 'phoA to the gene encoding RseB, a periplasmic negative regulator of the alternative sigma factor sigma(E). sigma(E) controls an extensive regulon involved in responding to cell envelope stresses. Colonies of the rseB mutant were less opaque than wild-type and underwent phase variation between translucent and opaque morphologies. rseB mutants were attenuated for virulence in subcutaneously inoculated iron dextran-treated mice. To gain insight into the role of rseB and the extracytoplasmic stress response in V. vulnificus, defined mutations in rseB and two important members of the extracytoplasmic stress regulon, rpoE and degP, were constructed for analysis of virulence, colony morphology, and stress-associated phenotypes. Deletion of rseB caused a reversible phase variation in colony morphotype that was associated with extracellular polysaccharides. Translucent and transparent morphotype strains were attenuated for virulence. Deletion mutants for rpoE and degP were sensitive to membrane-perturbing agents and heat but were not significantly attenuated for virulence of V. vulnificus in mice. These results reveal complex relationships between regulation of the extracytoplasmic stress response, exopolysaccharides, and virulence of V. vulnificus.
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