Fig 1.

SaeRS is required for expression of the nuc gene. (A) A plasmid containing the nuc promoter coupled to sGFP (pCM20) was transformed into the USA300 WT LAC and sae, agr, and sigB mutant strains. The WT strain with the empty vector was included as a negative control. GFP fluorescence was measured at 8, 12, 24, and 30 h and normalized to cell growth. Each value is the mean of three independent replicates, and error bars indicate the standard error of the mean. For statistical analysis, a one-way ANOVA was performed; statistical significance (P < 0.01) is indicated by an asterisk. (B) Relative nuc gene expression in USA300 strains grown in vitro. Data are normalized to gyrB transcript abundance, and n-fold change is relative to sae. WT LAC (black bars), the sae mutant (red bars), and the complemented (Comp) mutant strain (gray bars) were grown in TSB, and nuc expression was analyzed during mid-exponential-phase and early stationary-phase growth. Data are from two biological repetitions assayed in triplicate by TaqMan reverse transcription-PCR.