A PhoQ/P-regulated small RNA regulates sensitivity of Escherichia coli to antimicrobial peptides

Mol Microbiol. 2009 Dec;74(6):1314-30. doi: 10.1111/j.1365-2958.2009.06944.x. Epub 2009 Nov 2.


Non-coding small RNAs (sRNAs) play a major role in post-transcriptional regulation of gene expression. Of the 80 sRNAs that have been identified in E. coli, one-third bind to the RNA chaperone Hfq. Hfq both stabilizes these sRNAs in vivo and stimulates pairing to targets in vitro. A novel Hfq-dependent RNA, called here MgrR, was identified by its ability to bind Hfq. Expression of MgrR requires the PhoQ/PhoP two-component system; the PhoP response regulator is active under low Mg2+ concentrations and is an important virulence regulator in Salmonella; mgrR is also found in Salmonella species. Negatively regulated targets of MgrR identified using microarrays include eptB, involved in lipopolysaccharide (LPS) modification, and ygdQ, encoding a hypothetical protein. Cell sensitivity to the antimicrobial polymyxin B is affected by LPS modifications, and cells carrying an mgrR deletion were approximately 10 times more resistant than wild-type cells to polymyxin B. Thus, lower Mg2+ concentrations, sensed by PhoQ/PhoP, lead to expression of MgrR, changing LPS. sRNAs have previously been shown to regulate many outer membrane proteins. This work demonstrates that LPS, a major contributor of bacterial interactions with mammalian cells, is also subject to regulation by sRNAs.

Publication types

  • Research Support, N.I.H., Intramural

MeSH terms

  • Anti-Bacterial Agents / pharmacology*
  • Bacterial Proteins / physiology*
  • Base Sequence
  • Escherichia coli / drug effects
  • Escherichia coli / physiology*
  • Escherichia coli Proteins / metabolism
  • Escherichia coli Proteins / physiology*
  • Gene Deletion
  • Gene Expression Profiling
  • Gene Expression Regulation, Bacterial*
  • Host Factor 1 Protein / metabolism
  • Microbial Sensitivity Tests
  • Molecular Sequence Data
  • Oligonucleotide Array Sequence Analysis
  • Polymyxin B / pharmacology*
  • Protein Binding
  • RNA, Bacterial / biosynthesis*
  • RNA, Bacterial / genetics
  • RNA, Untranslated / biosynthesis*
  • RNA, Untranslated / genetics
  • Salmonella / genetics
  • Sequence Alignment


  • Anti-Bacterial Agents
  • Bacterial Proteins
  • Escherichia coli Proteins
  • Hfq protein, E coli
  • Host Factor 1 Protein
  • PhoP protein, E coli
  • PhoQ protein, Bacteria
  • RNA, Bacterial
  • RNA, Untranslated
  • Polymyxin B