FIGURE 4.

Transcription factor activity of toxR cysteine mutants. Shown are reporter gene activities of alkaline phosphatase PhoA (Miller Units) linked as operon fusions to either (a) ompU (white bars) or (b) ompT (black bars) in V. cholerae ΔdegP strains harboring various chromosomal cysteine mutations in toxR. Simultaneously, immunoblot analysis was performed under standard reducing Laemmli buffer conditions to detect OmpU or OmpT, respectively. Cells were grown in M9 maltose minimal medium and samples were taken in the mid‐log phase. V. cholerae ΔtoxR served as a negative control. The mean values with standard deviation are shown (n = 6). The asterisks indicate significantly different means with p < .05 for the respective columns each tested against ΔdegP toxR^WT using one‐way ANOVA test, followed by Dunnett's post hoc test for multiple comparisons. To note, all the characterized strains featured a chromosomally toxS⁺ background