Inducible prophages contribute to Salmonella virulence in mice.
We show that Salmonella typhimurium harbours two fully functional prophages, Gifsy-1 and Gifsy-2, that can be induced by standard treatments or, more effectively, by exposing bacteria to hydrogen peroxide. Curing bacteria for the Gifsy-2 prophage significantly reduces Salmonella's ability to establish a systemic infection in mice. Cured strains recover their virulence properties upon relysogenization. Phage Gifsy-2 carries the sodC gene for a periplasmic [Cu,Zn]-superoxide dismutase previously implicated in the bacterial defences against killing by macrophages. The contribution of the Gifsy-1 prophage to virulence - undetectable in the presence of Gifsy-2 as prophage - becomes significant in cells that lack Gifsy-2 but carry the sodC gene integrated in the chromosome. This confirms the involvement of Gifsy-2-encoded SodC protein in Salmonella pathogenicity and suggests that the Gifsy-1 prophage carries one or more additional virulence genes that have a functional equivalent on the Gifsy-2 genome.
Figueroa-Bossi
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Centre de Génétique Moléculaire, CNRS, 91198 Gif-sur-Yvette, France.
Bossi
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D000818:Animals; D001483:Base Sequence; D002876:Chromosomes, Bacterial / Q000235:genetics; D029968:Escherichia coli Proteins; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008242:Lysogeny; D051379:Mice; D016685:Mitomycin / Q000494:pharmacology; D008969:Molecular Sequence Data; D009268:Nalidixic Acid / Q000494:pharmacology; D012481:Salmonella Infections, Animal / Q000382:microbiology*; D012483:Salmonella Phages / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D012486:Salmonella typhimurium / Q000187:drug effects / Q000235:genetics / Q000472:pathogenicity / Q000821:virology*; D013482:Superoxide Dismutase / Q000235:genetics; D014774:Virulence / Q000235:genetics; D014775:Virus Activation / Q000187:drug effects
D029968:Escherichia coli Proteins; D009268:Nalidixic Acid; D016685:Mitomycin; D006861:Hydrogen Peroxide; D013482:Superoxide Dismutase; C116114:sodC protein, E coli