LytS-dependent expression of lrgAB in S . mutans . Overnight cultures were diluted in THYE, containing either 11 mM (A) or 45 mM glucose (B) to an OD600 = 0.02 and grown at 37°C as static cultures at 5% CO2 (“low-O2”) or as aerobic shaking cultures at 250 RPM (“aerobic”). RNA was harvested at exponential (EP) and stationary phase (SP). Reverse-transcription, real-time PCR reactions, and determination of copy number were performed as described previously using lrgA and 16S-specific primers [37, 77]. Fold-change expression of lrgAB and 16S under each growth condition was calculated by dividing the gene copy number of each test sample by the average gene copy number of UA159 EP. Data was then normalized by dividing each lrgAB fold-change value by its corresponding 16S fold-change expression value. Data represent the average of 3 biological replicates. Dark grey bars represent UA159 and light grey bars represent lytS mutant. Error Bars represent the standard error (SEM).