title: Increased expression of the multidrug efflux genes acrAB occurs during slow growth of Escherichia coli.
abstract: Intrinsic antimicrobial resistance of Escherichia coli is elicited by the gene products of the multidrug efflux acrAB-tolC operon. In this paper, we have shown that acrAB is regulated as a function of the growth rate of E. coli during growth in batch and chemostat culture. In chemostat culture, expression of acrAB is inversely related to growth rate irrespective of the limiting nutrient. The level of expression of acrAB is greater under glucose limitation compared with either iron or nitrogen limitation. Increase in expression of acrAB confers a greater resistance to ciprofloxacin, and the implications for a clinical situation are discussed. Slow growth rate regulation of acrAB transcription does not require the presence of the stationary-phase sigma factor. A putative gearbox consensus sequence was identified at the -10 region of the acrAB promoter.
authors.affiliation: Department of Biological Sciences, University of Central Lancashire, Preston PR1 2HE, UK.
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Rand
authors.forename: Simon G
authors.initials: SG
authors.lastname: Danby
authors.forename: David L A
authors.initials: DL
authors.lastname: Greenway
authors.forename: Reg R
authors.initials: RR
authors.lastname: England
mesh_terms: D000890:Anti-Infective Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins; D002939:Ciprofloxacin / Q000494:pharmacology; D003470:Culture Media; D024881:Drug Resistance, Bacterial; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D008074:Lipoproteins / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D000890:Anti-Infective Agents; D001426:Bacterial Proteins; D002352:Carrier Proteins; D002939:Ciprofloxacin; D003470:Culture Media; D029968:Escherichia coli Proteins; D008074:Lipoproteins; D008565:Membrane Proteins; 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