Post-transcriptional activation of a diguanylate cyclase by quorum sensing small RNAs promotes biofilm formation in Vibrio cholerae

Mol Microbiol. 2013 Sep;89(5):989-1002. doi: 10.1111/mmi.12325. Epub 2013 Jul 29.

Abstract

Biofilms promote attachment of Vibrio cholerae in aquatic ecosystems and aid in transmission. Intracellular c-di-GMP levels that control biofilm development positively correlate with expression of Qrr sRNAs, which are transcribed when quorum sensing (QS) autoinducer levels are low. The Qrr sRNAs base-pair with and repress translation of hapR encoding the QS 'master regulator', hence increased c-di-GMP and biofilm development at low density were believed to be solely a consequence of Qrr/hapR pairing. We show that Qrr sRNAs also base-pair with and activate translation of the mRNA of a diguanylate cyclase (DGC), Vca0939; relieving an inhibitory structure in vca0939 that occludes the ribosome binding site. A nucleotide substitution in vca0939 disrupted sRNA/mRNA base-pairing and prevented vca0939 translation, while a compensating Qrr sRNA substitution restored pairing and Vca0939 levels. Qrr-dependent DGC activation led to c-di-GMP accumulation and biofilm development in V. cholerae. This represents the first description of (1) a DGC post-transcriptionally activated by direct pairing with an Hfq-dependent sRNA, and (2) control of a V. cholerae QS phenotype, independent of HapR. Thus, direct interactions of the same sRNAs with two mRNAs promote c-di-GMP-dependent biofilm formation by complementary mechanisms in V. cholerae; by negatively regulating HapR, and positively regulating the DGC Vca0939.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Biofilms / growth & development*
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / metabolism*
  • Gene Expression Regulation, Bacterial*
  • Nucleic Acid Conformation
  • Phosphorus-Oxygen Lyases / genetics
  • Phosphorus-Oxygen Lyases / metabolism*
  • Point Mutation
  • Protein Biosynthesis
  • Quorum Sensing*
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • RNA, Small Untranslated / genetics
  • RNA, Small Untranslated / metabolism*
  • Vibrio cholerae / genetics
  • Vibrio cholerae / physiology*

Substances

  • Escherichia coli Proteins
  • RNA, Messenger
  • RNA, Small Untranslated
  • Phosphorus-Oxygen Lyases
  • diguanylate cyclase