Expression of toxR in the presence of AphA or AphB. (A). Activity of P
-luxCDABE reporter constructs (blue bars) in E. coli containing pBAD24 as a vector control, pBAD-aphA or pBAD-aphB. Arabinose (0.01%) was used to induce P
promoters and cultures were grown at 37°C to stationary phase. Units are arbitrary light units/OD600. The results are the average of three experiments ± SD. (B). toxR-lacZ expression (blue bars). V. cholerae lacZ- strains containing toxR-lacZ chromosomal transcriptional fusions and either pBAD24 or pBAD-aphB were grown in LB containing 0.01% arabinose at 37°C for 12 hrs and β-galactosidase activities of the cultures were measured  and reported as the Miller Unit. The results are the average of three experiments ± SD. (C). Analysis of samples in (B) by Western blot with anti-ToxR antiserum.