Sequence analysis of the Staphylococcus aureus srrAB loci reveals that truncation of srrA affects growth and virulence factor expression.

The SrrAB system regulates metabolism and virulence factors in Staphylococcus aureus. We sequenced the srrAB loci of 21 isolates and performed a phylogenetic analysis. Vaginal and bovine isolates clustered together, while skin isolates were genetically diverse. Few nucleotide polymorphisms were observed, and most were synonymous. Two strains (N2 and N19) with N-terminal truncations in SrrA displayed defects in growth and abnormally upregulated virulence factor expression under low-oxygen conditions.