Expression of <i>ctxA</i> in wild type, <i>vieA</i>, <i>vieSAB</i> and <i>hns</i> mutants.

<p>El Tor biotype WT and mutant strains containing a <i>ctxA-lacZ</i> promoter fusion were grown in ToxR-permissive AKI medium and non-permisive LB medium. β-galactosidase activity (Miller units) was measured as an indicator of promoter activity. Each value represents the mean of six independent experiments. Error bars denote the standard deviation (STDEV).