Identification of multiple σ54-dependent transcriptional activators in vibrio cholerae

Abstract

In the pathogenic bacterium Vibrio cholerae, the alternate sigma factor σ54 is required for expression of multiple sets of genes, including an unidentified gene(s) necessary for enhanced colonization within the host. To identify σ54-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 σ54-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 σ54-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 σ54-dependent activators not identified by this technique.