Identification of GtgE, a Novel Virulence Factor Encoded on the Gifsy-2 Bacteriophage ofSalmonella entericaSerovar Typhimurium

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Abstract
The Gifsy-2 temperate bacteriophage ofSalmonella entericaserovar Typhimurium contributes significantly to the pathogenicity of strains that carry it as a prophage. Previous studies have shown that Gifsy-2 encodes SodCI, a periplasmic Cu/Zn superoxide dismutase, and at least one additional virulence factor. Gifsy-2 encodes aSalmonellapathogenicity island 2 type III secreted effector protein. Sequence analysis of the Gifsy-2 genome also identifies several open reading frames with homology to those of known virulence genes. However, we found that null mutations in these genes did not individually have a significant effect on the ability ofS. entericaserovar Typhimurium to establish a systemic infection in mice. Using deletion analysis, we have identified a gene,gtgE, which is necessary for the full virulence ofS. entericaserovar Typhimurium Gifsy-2 lysogens. Together, GtgE and SodCI account for the contribution of Gifsy-2 toS. entericaserovar Typhimurium virulence in the murine model.