Role and regulation of the superoxide dismutases of Staphylococcus aureus

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Abstract
Staphylococcus aureushas two superoxide dismutases (SODs), encoded by thesodAandsodMgenes, which inactivate harmful superoxide radicals () encountered during host infection or generated from aerobic metabolism. The transcriptional start sites have been mapped and expression analysis on reporter fusions in both genes has been carried out. Under standard growth conditions, manganese (Mn), a mineral superoxide scavenger, elevated total SOD activity but had no effect on the transcription of either gene. Transcription ofsodAandsodMwas most strongly induced by either internally or externally generated, respectively. Sensitivity to internally generatedwas linked with SodA deficiency. Mn supplementation completely rescued asodAmutant when challenged by internally generated, and this was growth-phase-dependent. Sensitivity to externally generatedstress was only observed in asodA sodMmutant and was Mn-independent. In a mouse abscess model of infection, isogenicsodA,sodMandsodAsodMmutants had reduced virulence compared to the parental strain, showing the importance of the enzymicscavenging system for the survival of the pathogen.

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