Evidence for a coordinate transcriptional control of alpha-toxin and protein a synthesis inStaphylococcus aureus

A spontaneous mutant (Exp) of Staphylococcus aureus V8 with a decreased α-toxin production and a simultaneously increased production of protein A was analyzed for α-toxin and protein A-specific mRNAs. The mutant had a 20-fold decrease in α-toxin mRNA and a 60-fold increase in protein A mRNA as compared to the wild-type strain. Both in the mutant and in the wild type the differential rate of exoprotein production increased during the post-exponential growth phase. The increase in rates of α-toxin and protein A production was due to increased transcription of these genes, indicating that there are two independent mechanisms of exoprotein regulation in S. aureus; one dependent on the exp gene and another which is growth rate dependent.