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Escherichia coli mar and acrAB Mutants Display No Tolerance to Simple Alcohols
Bioorganic & Biophysical Chemistry Laboratory, School of Natural Sciences, Linnaeus University, SE-391 82 Kalmar, Sweden
Department of Biochemistry & Organic Chemistry, Uppsala University, Box 576, SE-751 23 Uppsala, Sweden
* Author to whom correspondence should be addressed.
Received: 1 February 2010; in revised form: 28 March 2010 / Accepted: 29 March 1995 / Published: 31 March 2010
Abstract: The inducible Mar phenotype of Escherichia coli is associated with increased tolerance to multiple hydrophobic antibiotics as well as some highly hydrophobic organic solvents such as cyclohexane, mediated mainly through the AcrAB/TolC efflux system. The influence of water miscible alcohols ethanol and 1-propanol on a Mar constitutive mutant and a mar deletion mutant of E. coli K-12, as well as the corresponding strains carrying the additional acrAB deletion, was investigated. In contrast to hydrophobic solvents, all strains were killed in exponential phase by 1-propanol and ethanol at rates comparable to the parent strain. Thus, the Mar phenotype does not protect E. coli from killing by these more polar solvents. Surprisingly, AcrAB does not contribute to an increased alcohol tolerance. In addition, sodium salicylate, at concentrations known to induce the mar operon, was unable to increase 1-propanol or ethanol tolerance. Rather, the toxicity of both solvents was increased in the presence of sodium salicylate. Collectively, the results imply that the resilience of E. coli to water miscible alcohols, in contrast to more hydrophobic solvents, does not depend upon the AcrAB/TolC efflux system, and suggests a lower limit for substrate molecular size and functionality. Implications for the application of microbiological systems in environments containing high contents of water miscible organic solvents, e.g.,phage display screening, are discussed.
Keywords: solvent tolerance; salicylate; ethanol; 1-propanol; mar regulon; hydrophobicity; solvent
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Ankarloo, J.; Wikman, S.; Nicholls, I.A. Escherichia coli mar and acrAB Mutants Display No Tolerance to Simple Alcohols. Int. J. Mol. Sci. 2010, 11, 1403-1412.
Ankarloo J, Wikman S, Nicholls IA. Escherichia coli mar and acrAB Mutants Display No Tolerance to Simple Alcohols. International Journal of Molecular Sciences. 2010; 11(4):1403-1412.
Ankarloo, Jonas; Wikman, Susanne; Nicholls, Ian A. 2010. "Escherichia coli mar and acrAB Mutants Display No Tolerance to Simple Alcohols." Int. J. Mol. Sci. 11, no. 4: 1403-1412.