title: Role of the acrAB locus in organic solvent tolerance mediated by expression of marA, soxS, or robA in Escherichia coli.
abstract: Escherichia coli K-12 strains are normally tolerant to n-hexane and susceptible to cyclohexane. Constitutive expression of marA of the multiple antibiotic resistance (mar) locus or of the soxS or robA gene product produced tolerance to cyclohexane. Inactivation of the mar locus or the robA locus, but not the soxRS locus, increased organic solvent susceptibility in the wild type and Mar mutants (to both n-hexane and cyclohexane). The organic solvent hypersusceptibility is a newly described phenotype for a robA-inactivated strain. Multicopy expression of mar, soxS, or robA induced cyclohexane tolerance in strains with a deleted or inactivated chromosomal mar, soxRS, or robA locus; thus, each transcriptional activator acts independently of the others. However, in a strain with 39 kb of chromosomal DNA, including the mar locus, deleted, only the multicopy complete mar locus, consisting of its two operons, produced cyclohexane tolerance. Deletion of acrAB from either wild-type E. coli K-12 or a Mar mutant resulted in loss of tolerance to both n-hexane and cyclohexane. Organic solvent tolerance mediated by mar, soxS, or robA was not restored in strains with acrAB deleted. These findings strongly suggest that active efflux specified by the acrAB locus is linked to intrinsic organic solvent tolerance and to tolerance mediated by the marA, soxS, or robA gene product in E. coli.
authors.affiliation: Center for Adaptation Genetics and Drug Resistance and Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
authors.forename: D G
authors.initials: DG
authors.lastname: White
authors.forename: J D
authors.initials: JD
authors.lastname: Goldman
authors.forename: B
authors.initials: B
authors.lastname: Demple
authors.forename: S B
authors.initials: SB
authors.lastname: Levy
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics*; D002352:Carrier Proteins; D003510:Cyclohexanes / Q000494:pharmacology*; D004268:DNA-Binding Proteins / Q000235:genetics*; D004352:Drug Resistance, Microbial / Q000235:genetics; D004361:Drug Tolerance / Q000235:genetics; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development; D029968:Escherichia coli Proteins; D015870:Gene Expression; D006586:Hexanes / Q000494:pharmacology*; D008074:Lipoproteins / Q000235:genetics; D008565:Membrane Proteins / Q000235:genetics; D026901:Membrane Transport Proteins; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009876:Operon; D012997:Solvents / Q000494:pharmacology; D015534:Trans-Activators; D014157:Transcription Factors / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D003510:Cyclohexanes; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D006586:Hexanes; D008074:Lipoproteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D012997:Solvents; D015534:Trans-Activators; D014157:Transcription Factors; C083497:AcrA protein, E coli; C083496:AcrB protein, E coli; C080002:MarA protein, E coli; C080267:Rob protein, E coli; C070725:SoxS protein, E coli