RESEARCH ARTICLE RNA-Seq Analysis Identifies New Genes Regulated by the Histone-Like Nucleoid Structuring Protein (H-NS) Affecting Vibrio cholerae Virulence, Stress Response and

The histone-like nucleoid structuring protein (H-NS) functions as a transcriptional silencer by binding to AT-rich sequences at bacterial promoters. However, H-NS repression can be counteracted by other transcription factors in response to environmental changes. The identification of potential toxic factors, the expression of which is prevented by H-NS could facilitate the discovery of new regulatory proteins that may contribute to the emergence of new pathogenic variants by anti-silencing. Vibrio cholerae hnsmutants of the El Tor biotype exhibit altered virulence, motility and environmental stress response phenotypes compared to wild type. We used an RNA-seq analysis approach to determine the basis of the above hns phenotypes and identify new targets of H-NS transcriptional silencing. H-NS affected the expression of 18 % of all predicted genes in a growth phase-dependent manner. Loss of H-NS resulted in diminished expression of numerous genes encoding methyl-accepting chemotaxis proteins as well as chemotaxis toward the attractants glycine and serine. Dele-tion of hns also induced an endogenous envelope stress response resulting in elevated ex-pression of rpoE encoding the extracytoplamic sigma factor E (σE). The RNA-seq analysi