Fig 4.

sigS transcription is inducible in response to external stress. (A to C) The 8325-4 sigS-lacZ strain was grown in either TSB (✦) or TSB supplemented with sublethal concentrations of the indicated stress chemicals (■). Cultures were sampled every hour for 10 h, and again at 24 h, to determine β-galactosidase activity. Additionally, growth was monitored via OD₆₀₀ at the times indicated for both standard (♢) and supplemented (□) growth conditions. Assays were performed on duplicate samples and the values averaged. The results presented here were representative of three independent replicates that showed less than 10% variability. (D) Quantitative real-time PCR analysis was performed with strain 8325-4 grown for 5 h under conditions identical to those described for panels A to C, using primers specific to sigS. The data presented are from at least 3 independent experiments. Error bars indicate ± standard error of the mean; *, P < 0.05 by the Student t test.