CrbS/R controls expression of <i>acsA</i> in a non-O1/non-O139 strain of <i>V</i>. <i>cholerae</i>.

<p>Expression of the <i>luxCDABE</i> operon driven by the <i>V</i>. <i>cholerae</i> SIO <i>acsA</i> promoter in plasmid pPT002 was measured after 4, 8, and 10 hours of growth, and normalized to OD_600nm. The pBBRlux plasmid carries no promoter sequence. Luminescence was measured in <i>V</i>. <i>cholerae</i> strains carrying in-frame deletions of <i>crbS</i>, <i>crbR</i>, or the receiver domain of <i>crbR</i> (A); in <i>V</i>. <i>cholerae</i> strains with mutations in the putative conserved histidine within the HisKA domain (H798A and H798Q) (B); and in <i>V</i>. <i>cholerae</i> strains carrying either an in-frame deletion of the <i>crbS</i> receiver domain or a mutation within the putative conserved aspartate residue in the <i>crbS</i> receiver domain (D1081A) (C). Results from two biological replicates, each performed in duplicate or triplicate, are shown. Statistical significance was determined by comparing results from each mutant strain to those of the wild-type strain at that time point using the Mann-Whitney test. (*) denotes a P-value less than 0.05, (**) denotes a P-value less than 0.01, and (***) denotes a P-value less than 0.001.