FIG 6.

C18-depleted AKI medium abolishes the RND efflux-dependent induction of ompR expression in V. cholerae. (A) WT and ΔRND V. cholerae strains harboring an ompR-lacZ reporter plasmid (pDK9) were cultured in the indicated media for 5 h when ompR-lacZ expression was quantified. *, P < 0.01 relative to WT determined by a t test. (B) WT and ΔRND V. cholerae strains were cultured under AKI conditions in either an AKI medium or a C18-depleted AKI medium for 24 h when CT and TcpA production was assessed by GM1 ELISA and TcpA immunoblotting, respectively. Data represent the mean ± SD of three independent experiments. *, P < 0.01 relative to AKI, determined by t test. C18-depleted AKI medium and C18 column AKI medium eluates were prepared as described in Materials and Methods.