Fig 4. RsbR1 residues T209 and T241 are required for normal acid-mediated activation of σ^B and development of acid tolerance.

Expression of σ^B-dependent genes (A) lmo2230 and (B) lmo0596, obtained from mid-log phase cultures of wild type and rsbR1 (T175A), rsbR1 (T209A) and rsbR1 (T241A) strains untreated (-) and treated (+) for 15 min in pH 5.0 at 37°C. Gene expression is expressed as Log₂ relative gene expression. Acid challenge of mid-log phase of (C) rsbR1 (T175A), (D) rsbR1 (T209A) and (E) rsbR1 (T241A) cultures treated in pH 5.0 for 15 min at 37°C, as previously described in Fig 2D. Survival data is expressed as Log₁₀ (CFU.mL^-1). Statistical analysis was performed using a paired Student’s t-test relative to the wild type untreated after 15 min, for RT-qPCR data, and untreated wild type at time 0 min, for acid challenge data (*, P value of <0.05; **, P value of <0.01; ***, P value of <0.001).