Quorum sensing and multidrug transporters in Escherichia coli.
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.
Yang
Shirley
S
Department of Molecular Virology and Microbiology and Interdepartmental Program in Cell and Molecular Biology, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX 77030, USA.
Lopez
Christopher R
CR
Zechiedrich
E Lynn
EL
D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000502:physiology; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology; D013437:Carbon-Sulfur Lyases; D017077:Culture Media, Conditioned; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000502:physiology*; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial / Q000235:genetics*; D008074:Lipoproteins / Q000235:genetics / Q000502:physiology*; D026901:Membrane Transport Proteins; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics / Q000502:physiology*; D009154:Mutation; D012808:Sigma Factor / Q000235:genetics; D015533:Transcriptional Activation
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D013437:Carbon-Sulfur Lyases; D017077:Culture Media, Conditioned; D029968:Escherichia coli Proteins; D008074:Lipoproteins; D026901:Membrane Transport Proteins; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D012808:Sigma Factor; C083497:AcrA protein, E coli; C083496:AcrB protein, E coli; C069567:sigma factor KatF protein, Bacteria; C073126:tolC protein, E coli; C117753:LuxS protein, Bacteria