Comparison of MRSA USA300 WT and srrAB mutant in atmospheric and low O2/CO2 growth

AH1263 WT and srrAB mutant strains were grown in TSB to mid-log (OD600=0.5) and used as an input. Subcultures were either grown shaking at 37 to late-log (OD600=1.5) or static at 37 in a sealed container with CO2 GasPak (OD600=0.5). In the GasPak container, CO2 concentration was estimated at > 18mmHg and the oxygen concentration at ~125mmHg. These levels are comparable to those found in the human vaginal tract during the non-menstrual mid-cycle and during periods of low menstrual load. Comparisons of transcript levels between samples can be used to identify transcriptional differences between WT MRSA and MRSA without a functional SrrAB two-component system under various in vitro conditions, including those relevant to vaginal colonization.