Abstract
Growth of Escherichia coli is inhibited upon exposure to a large volume of a harmful solvent, and there is an inverse correlation between the degree of inhibition and the log P(OW) of the solvent, where P(OW) is the partition coefficient measured for the partition equilibrium established between the n-octanol and water phases. The AcrAB-TolC efflux pump system is involved in maintaining intrinsic solvent resistance. We inspected the solvent resistance of delta acrAB and/or delta tolC mutants in the presence of a large volume of solvent. Both mutants were hypersensitive to weakly harmful solvents, such as nonane (log P(OW) = 5.5). The delta tolC mutant was more sensitive to nonane than the delta acrAB mutant. The solvent entered the E. coli cells rapidly. Entry of solvents with a log P(OW) higher than 4.4 was retarded in the parent cells, and the intracellular levels of these solvents were maintained at low levels. The delta tolC mutant accumulated n-nonane or decane (log P(OW) = 6. 0) more abundantly than the parent or the delta acrAB mutant. The AcrAB-TolC complex likely extrudes solvents with a log P(OW) in the range of 3.4 to 6.0 through a first-order reaction. The most favorable substrates for the efflux system were considered to be octane, heptane, and n-hexane.
MeSH terms
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Alkanes / metabolism*
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Alkanes / pharmacology
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Bacterial Outer Membrane Proteins / genetics
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Bacterial Outer Membrane Proteins / metabolism*
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Bacterial Proteins / genetics
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Bacterial Proteins / metabolism*
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Base Sequence
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Carrier Proteins / genetics
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Carrier Proteins / metabolism*
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Culture Media
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DNA, Bacterial
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Drug Resistance, Microbial
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Escherichia coli / drug effects
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Escherichia coli / genetics
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Escherichia coli / growth & development
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Escherichia coli / metabolism*
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Escherichia coli Proteins*
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Genes, Bacterial
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Intracellular Fluid / metabolism
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Lipoproteins / genetics
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Lipoproteins / metabolism*
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Membrane Proteins / genetics
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Membrane Proteins / metabolism*
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Membrane Transport Proteins
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Molecular Sequence Data
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Multidrug Resistance-Associated Proteins
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Solvents / metabolism*
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Solvents / pharmacology
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Substrate Specificity
Substances
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AcrA protein, E coli
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AcrB protein, E coli
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Alkanes
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Bacterial Outer Membrane Proteins
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Bacterial Proteins
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Carrier Proteins
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Culture Media
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DNA, Bacterial
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EmrA protein, E coli
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Escherichia coli Proteins
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Lipoproteins
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Membrane Proteins
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Membrane Transport Proteins
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Multidrug Resistance-Associated Proteins
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Solvents
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tolC protein, E coli
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emrA protein, Bacteria
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VceB protein, Vibrio cholerae
Associated data
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GENBANK/AB005476
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GENBANK/AB005477
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GENBANK/AB005478