FIG 2.

OmpR represses virulence factor production in RND efflux-negative V. cholerae. (A) WT and ΔRND V. cholerae strains harboring an ompR-lacZ reporter plasmid were cultured under the indicated conditions for 5 h when β-galactosidase activity was quantified. Data represent the mean ± SD of three independent experiments performed in triplicate. *, P < 0.0001 relative to WT determined by a t test. (B) The indicated V. cholerae strains were cultured under AKI conditions with the ΔRNDΔompR::pBAD33-ompR strain cultured in the presence of 0.05% arabinose. At 24 h, culture samples were collected, and CT and TcpA production was assessed by GM1 ELISA and TcpA immunoblotting, respectively. The CT data represent the mean ± SD of a minimum of three independent experiments. ND, nondetectable levels of CT. *, P < 0.05; **, P < 0.01 relative to the parental strain, determined by Tukey’s multiple-comparison test. TcpA immunoblot is representative of a minimum of three independent experiments.