Identification of Multiple ς 54 -Dependent Transcriptional Activators in Vibrio cholerae

Abstract

ABSTRACT In the pathogenic bacterium Vibrio cholerae , the alternate sigma factor ς 54 is required for expression of multiple sets of genes, including an unidentified gene(s) necessary for enhanced colonization within the host. To identify ς 54 -dependent transcriptional activators involved in colonization, PCR was performed with V. cholerae chromosomal DNA and degenerate primers, revealing six novel and distinct coding sequences with homology to ς 54 -dependent activators. One sequence had high homology to the luxO gene of V. harveyi , which in that organism is involved in quorum sensing. Phenotypes of V. cholerae strains containing mutations in each of the six putative ς 54 -dependent activator genes identified one as a probable ntrC homologue. None of the mutant strains exhibited a defect in the ability to colonize infant mice, suggesting the presence of additional ς 54 -dependent activators not identified by this technique.