Superoxide dismutase B gene (sodB)-deficient mutants of Francisella tularensis demonstrate hypersensitivity to oxidative stress and attenuated virulence.

A Francisella tularensis live vaccine strain mutant (sodB(Ft)) with reduced Fe-superoxide dismutase gene expression was generated and found to exhibit decreased sodB activity and increased sensitivity to redox cycling compounds compared to wild-type bacteria. The sodB(Ft) mutant also was significantly attenuated for virulence in mice. Thus, this study has identified sodB as an important F. tularensis virulence factor.