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J Appl Microbiol. 2004;96(6):1237-44.

Comparison of the glutamate-, arginine- and lysine-dependent acid resistance systems in Escherichia coli O157:H7.

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1
Department of Food Science and Nutrition, University of Minnesota, St Paul, MN, USA. fdiez@umn.edu

Abstract

AIMS:

The objective of this study was to investigate the effect of growing conditions on the glutamate-, arginine- and lysine-dependent acid resistance (AR) systems of Escherichia coli O157:H7.

METHODS AND RESULTS:

Seven E. coli O157:H7 strains were grown in five different media at neutral or acidic pH under aerobic or anaerobic conditions, and the survival rate after acid shocks (pH 2.0, 1 h, 37 degrees C) in the presence of glutamate, arginine and lysine was determined. Six strains induced the glutamate-dependent AR at stationary phase, and maximal survival were observed (> or =10%) when grown in pH 5- Luria-Bertani media with glucose (LBG) and in pH 4.5-anaerobic media. The arginine- and lysine-dependent systems were also present, but were only induced if cells had grown in LBG. For strain ATCC 43895, the minimum glutamate concentration that resulted in at least 10% survival rate was 10 micromol l(-1), but it required at least 10-fold more arginine and lysine.

CONCLUSIONS:

The lysine-dependent AR system could be as important as the arginine-mediated one, but the contribution of both systems to E. coli O157:H7 overall AR response might be minor compared with the glutamate-dependent system.

SIGNIFICANCE AND IMPACT OF THE STUDY:

Under typical environmental conditions, the glutamate-dependent AR system might be solely responsible for protecting cells against acidic pH.

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