Quorum sensing and multidrug transporters in Escherichia coli

Proc Natl Acad Sci U S A. 2006 Feb 14;103(7):2386-91. doi: 10.1073/pnas.0502890102. Epub 2006 Feb 7.


Previously, we found that the quorum sensing transcription factor SdiA up-regulates AcrAB. Others found that a 4-quinolone was a quorum-sensing signal in Pseudomonas aeruginosa. In Escherichia coli, there are at least three multidrug transporters (AcrAB/TolC, MdfA, and NorE) that exude fluoroquinolones. Here, we show that DeltaacrAB, tolC210, or DeltanorE mutants have the same growth rate as WT cells in exponential phase but grow to higher cell density in stationary phase. Overproduction of either pump caused cells to reach lower density. mdfA had no effect. Conditioned medium (CM) from cells overexpressing acrAB represses cell growth more than CM from WT cells. CM from pump mutant cells represses cell growth less than CM from WT cells. These results were not affected by the deletion of luxS, which synthesizes the quorum-sensing signal autoinducer 2 (AI-2). Expression of the rpoS gene encoding the stationary phase sigma factor is induced earlier in cells overexpressing acrAB and later in acrAB mutant cells. These results support a model in which a natural function of AcrAB/TolC and NorE is to export signals for cell-cell communication. Drugs exported by pumps may resemble communication molecules normally exuded.

Publication types

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

MeSH terms

  • Bacterial Outer Membrane Proteins / genetics
  • Bacterial Outer Membrane Proteins / physiology
  • Bacterial Proteins / genetics
  • Bacterial Proteins / physiology
  • Carbon-Sulfur Lyases
  • Culture Media, Conditioned
  • Drug Resistance, Multiple, Bacterial / genetics
  • Escherichia coli / genetics*
  • Escherichia coli / growth & development*
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / physiology*
  • Gene Deletion
  • Gene Expression Regulation, Bacterial
  • Genes, Bacterial / genetics*
  • Lipoproteins / genetics
  • Lipoproteins / physiology*
  • Membrane Transport Proteins
  • Multidrug Resistance-Associated Proteins / genetics
  • Multidrug Resistance-Associated Proteins / physiology*
  • Mutation
  • Sigma Factor / genetics
  • Transcriptional Activation


  • AcrA protein, E coli
  • AcrB protein, E coli
  • Bacterial Outer Membrane Proteins
  • Bacterial Proteins
  • Culture Media, Conditioned
  • Escherichia coli Proteins
  • Lipoproteins
  • Membrane Transport Proteins
  • Multidrug Resistance-Associated Proteins
  • Sigma Factor
  • sigma factor KatF protein, Bacteria
  • tolC protein, E coli
  • Carbon-Sulfur Lyases
  • LuxS protein, Bacteria