FIG 2 .

Effect of leuO on CT and TcpA production. The indicated strains were grown overnight under AKI conditions, normalized by OD, and used for CT ELISA and TcpA Western blotting. (A) CT and TcpA production in the WT (pBAD18) or WT (pBAD-leuO) strain grown with 0.02% or 0.08% arabinose. (B) CT and TcpA production in the WT and the ΔleuO mutant. The results are representative of three experiments ± SD. (C) Schematic diagram of the V. cholerae leuO locus. The gene encoding LeuO (VC2485) is downstream from VC2486 in an apparent two-gene operon. VC2486 and leuO are separated by 15 nucleotides (nt) and appear to be expressed from a common promoter that is located upstream of VC2486. The two ToxR-binding site consensus sequences in the leuO promoter are indicated by the yellow boxes.