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Journal of Bacteriology, September 2000, p. 4803-4810, Vol. 182, No. 17
Department of Biological Information,
Graduate School of Bioscience and Biotechnology, Tokyo Institute of
Technology, Nagatsuta 4259, Midori-ku, Yokohama 226-8501, Japan
Received 10 November 1999/Accepted 12 June 2000
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
POW of the solvent, where
POW 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
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Entry into and Release of Solvents by
Escherichia coli in an Organic-Aqueous Two-Liquid-Phase
System and Substrate Specificity of the AcrAB-TolC
Solvent-Extruding Pump
acrAB and/or
tolC mutants
in the presence of a large volume of solvent. Both mutants were
hypersensitive to weakly harmful solvents, such as nonane (log
POW = 5.5). The
tolC mutant
was more sensitive to nonane than the
acrAB mutant. The
solvent entered the E. coli cells rapidly. Entry of
solvents with a log POW higher than 4.4 was
retarded in the parent cells, and the intracellular levels of these
solvents were maintained at low levels. The
tolC mutant accumulated n-nonane or decane (log
POW = 6.0) more abundantly than the parent
or the
acrAB mutant. The AcrAB-TolC complex likely extrudes solvents with a log POW 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.
*
Corresponding author. Mailing address: Department of
Biological Information, Graduate School of Bioscience and
Biotechnology, Tokyo Institute of Technology, Nagatsuta 4259, Midori-ku, Yokohama 226-8501, Japan. Phone: (81) 45-924-5766. Fax: (81)
45-924-5819. E-mail: raono{at}bio.titech.ac.jp.
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