FIG 7.

RcsB positively regulates acid resistance in S. marcescens. (A) Spot assays show that RcsB is required for S. marcescens to grow under low-pH conditions (pH 4.0). (B) Growth curves of the JNB5-1, SK68, SK68/pXW1908, ΔRcsB, and ΔRcsB/pXW1908 strains at pH 4.0. (C) Changes in acid resistance-related gene expression in the rcsB-disrupted mutant SK68 compared with that in the parent strain JNB5-1 at pH 4.0. The speA, SMDB11_RS08645, argF, and cadC genes encode arginine decarboxylase, agmatine deiminase, ornithine transcarbamylase, and transcriptional activator CadC, respectively. (B and C) Experiments were performed in biological triplicates. Error bars indicate the standard deviations. One-way ANOVA was used to examine the mean differences between the data groups. ****, P < 0.001.