GSE62785
RNA-seq Analysis Identifies New Genes Regulated by the Histone-like Nucleoid Structuring Protein (H-NS) Affecting Vibrio cholerae Virulence, Stress Response and Chemotaxis
Cholera is a diarrheal disease caused by Vibrio cholerae of serogroups O1 and O139 that affects impoverished populations worldwide. The histone-like nucleoid structuring protein (H-NS) is a global regulator of environmentally-regulated gene expression that plays a fundamental role in V. cholerae adaptation to disparate ecological niches. We used RNA-seq to characterize the hns transcriptome of El Tor biotype V. cholerae. H-NS affected the expression of 18% of all predicted genes in a growth phase-dependent manner. It silenced the transcription of genes encoding virulence regulators and cytotoxic factors such as the VieSAB regulatory system, the repeat in toxin (RTX) and hemolysin. H-NS was 10 times more effective in silencing the vieSAB promoter in El Tor compared to classical biotype V. cholerae. In the El Tor biotype hns mutant, VieSAB significantly enhanced the expression of cholera toxin genes.  For the RTX and hemolysin, we found that overexpression of the transcription activator HlyU diminished H-NS occupancy at the hlyA promoter but not at the rtxCA and rtxBDE promoters. H-NS had a significant impact on the cell envelope and the mutant expressed elevated rpoE encoding the extracytoplamic sigma factor E (sE), though this effect was indirect. A remarkable feature of the hns transcriptome was the down-regulation of numerous methyl-accepting chemotaxis proteins in early stationary phase that translated into diminished chemotaxis toward the amino acids glycine and serine. Our study suggests that H-NS transcriptional silencing can contribute to multiple phenotypic differences observed between V. cholerae biotypes, mainly by differentially repressing the VieSAB sensory pathway. Overall design: Transcriptome profiles of wild type and ?hns mutant cells of the V. cholerae strain C7258 grown in LB medium were generated by Next Generation Sequencing using the Illumina HiSeq2000 platform. Samples from mid-exponential phase (OD600 0.5) and early stationary phase (OD600 2.0) were analyzed in duplicate