Quorum regulatory small RNAs repress type VI secretion in Vibrio cholerae. Author Yi Shao, Bonnie Bassler Publication Year 2014 Type Journal Article Abstract Type VI secretion is critical for Vibrio cholerae to successfully combat phagocytic eukaryotes and to survive in the presence of competing bacterial species. V. cholerae type VI secretion system genes are encoded in one large and two small clusters. In V. cholerae, type VI secretion is controlled by quorum sensing, the cell-cell communication process that enables bacteria to orchestrate group behaviours. The quorum-sensing response regulator LuxO represses type VI secretion genes at low cell density and the quorum-sensing regulator HapR activates type VI secretion genes at high cell density. We demonstrate that the quorum regulatory small RNAs (Qrr sRNAs) that function between LuxO and HapR in the quorum-sensing cascade are required for these regulatory effects. The Qrr sRNAs control type VI secretion via two mechanisms: they repress expression of the large type VI secretion system cluster through base pairing and they repress HapR, the activator of the two small type VI secretion clusters. This regulatory arrangement ensures that the large cluster encoding many components of the secretory machine is expressed prior to the two small clusters that encode the secreted effectors. Qrr sRNA-dependent regulation of the type VI secretion system is conserved in pandemic and non-pandemic V. cholerae strains. Keywords Gene Expression Regulation, Bacterial, Quorum Sensing, Vibrio cholerae, Bacterial Proteins, RNA, Bacterial Journal Mol Microbiol Volume 92 Issue 5 Pages 921-30 Date Published 2014 Jun ISSN Number 1365-2958 DOI 10.1111/mmi.12599 Alternate Journal Mol Microbiol PMCID PMC4038675 PMID 24698180 PubMedPubMed CentralGoogle ScholarBibTeXEndNote X3 XML