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Res Microbiol. 2008 Jul-Aug;159(6):458-61. doi: 10.1016/j.resmic.2008.04.011. Epub 2008 May 9.

Cyclopropane fatty acids improve Escherichia coli survival in acidified minimal media by reducing membrane permeability to H+ and enhanced ability to extrude H+.

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Food Safety Centre, Tasmanian Institute of Agricultural Research, School of Agricultural Science, University of Tasmania, Private Bag 54, Hobart, Tas 7001, Australia.


The physiological role of cyclopropane fatty acids (CFAs) in acid stress resistance was studied by in situ microelectrode H+ flux measurements of Escherichia coli Frag1 and its isogenic CFA-deficient mutant JBM 1. After exposure to pH 4 for 16h, net H+ influx in JBM 1 was twice that of the parent strain. H+ flux stabilisation at pH 6 after acid stress took more time in the cfa- mutant. The data suggest increased proton permeability and decreased ability to extrude H+ in the absence of CFA, and they support the hypothesis that CFAs protect E. coli in acidic environments by decreasing membrane permeability to H+.

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