Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 103, Issue 7, Pages 2386-2391Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0502890102
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Funding
- NCI NIH HHS [CA09197, T32 CA009197] Funding Source: Medline
- NIAID NIH HHS [R01 AI054830] Funding Source: Medline
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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/ToIC, MdfA, and NorE) that exude fluoroquinolones. Here, we show that Delta acrAB, toIC210, or Delta norE 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/ToIC and NorE is to export signals for cell-cell communication. Drugs exported by pumps may resemble communication molecules normally exuded.
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