FIG. 1.

hchA is induced by oxidative (A) and acid (B) stresses. The hchA::lacZ lysogens MIR510 (wild type [wt]), MIR512 (rpoS359), MIR514 (Δhns), and MIR516 (Δhns rpoS359) were grown to mid-exponential phase in LB-streptomycin medium at 37°C (preinduction) and treated with either 0.005% hydrogen peroxide or left untreated (A). Acid shock experiments (B) were conducted with late-exponential-phase cells as described in the text. Samples were collected 1 h after challenge, and clarified lysates were assayed for β-galactosidase activities (top panels), while whole-cell fractions were analyzed by immunoblotting with Hsp31 antiserum (bottom panels). Numbers above columns correspond to n-fold induction levels relative to isogenic, unstressed controls. Single asterisks denote a P value of 0.05 or less, while double asterisks denote a P value of 0.005 or less. Labels below blots identify prestress samples (lanes 1) and samples from cultures grown for 1 h without stress (lanes 2) or with imposed stress (lanes 3). Error bars were obtained for triplicate independent experiments.