FIG 5.

Effect of tolC on the expression of the V. cholerae RND efflux systems. (A) The expression level of the genes encoding the six V. cholerae RND-family pump proteins in the ΔtolC mutant relative to the WT. V. cholerae WT and ΔtolC strains were cultured under AKI conditions for 5 h, and total RNA was isolated and used to assess the expression level of the indicated genes by qRT-PCR as described in Materials and Methods. The results are the means and standard deviations from three independent experiments. Statistical significance was determined by the t test relative to a hypothetical fold change of 1.0. *, P ≤ 0.05. (B and C) Expression of aphA and ctxA in WT, ΔtolC, ΔRND, and ΔRND ΔtolC strains following growth under AKI conditions for 5 h. The indicated strains bearing aphA-lux (B) or ctxA-lux (C) reporters were cultured under AKI conditions for 5 h, when reporter gene expression was quantified as relative light units (RLU) and normalized by the optical density at 600 nm. The results are the means and standard deviations from three independent experiments. Statistical significance was determined using ANOVA with the Tukey-Kramer multiple-comparison test. *, P ≤ 0.05 relative to the WT.