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Applied and Environmental Microbiology, December 2002, p. 5965-5972, Vol. 68, No. 12
0099-2240/02/$04.00+0     DOI: 10.1128/AEM.68.12.5965-5972.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.

Role of Membrane Fluidity in Pressure Resistance of Escherichia coli NCTC 8164

M. A. Casadei,{dagger} P. Mañas, G. Niven, E. Needs, and B. M. Mackey*

School of Food Biosciences, University of Reading, Whiteknights, Reading RG6 6AP, United Kingdom

Received 6 May 2002/ Accepted 16 September 2002

The relationship among growth temperature, membrane fatty acid composition, and pressure resistance was examined in Escherichia coli NCTC 8164. The pressure resistance of exponential-phase cells was maximal in cells grown at 10°C and decreased with increasing growth temperatures up to 45°C. By contrast, the pressure resistance of stationary-phase cells was lowest in cells grown at 10°C and increased with increasing growth temperature, reaching a maximum at 30 to 37°C before decreasing at 45°C. The proportion of unsaturated fatty acids in the membrane lipids decreased with increasing growth temperature in both exponential- and stationary-phase cells and correlated closely with the melting point of the phospholipids extracted from whole cells examined by differential scanning calorimetry. Therefore, in exponential-phase cells, pressure resistance increased with greater membrane fluidity, whereas in stationary-phase cells, there was apparently no simple relationship between membrane fluidity and pressure resistance. When exponential-phase or stationary-phase cells were pressure treated at different temperatures, resistance in both cell types increased with increasing temperatures of pressurization (between 10 and 30°C). Based on the above observations, we propose that membrane fluidity affects the pressure resistance of exponential- and stationary-phase cells in a similar way, but it is the dominant factor in exponential-phase cells whereas in stationary-phase cells, its effects are superimposed on a separate but larger effect of the physiological stationary-phase response that is itself temperature dependent.

* Corresponding author. Mailing address: School of Food Biosciences, University of Reading, P.O. Box 226, Whiteknights, Reading RG6 6AP, United Kingdom. Phone: 44 1189 357 229. Fax: 44 1189 357 222. E-mail: b.m.mackey{at}reading.ac.uk.

{dagger} Present address: Via Rocca 27, Meldola, 47014 Forli, Italy.

Applied and Environmental Microbiology, December 2002, p. 5965-5972, Vol. 68, No. 12
0099-2240/02/$04.00+0     DOI: 10.1128/AEM.68.12.5965-5972.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.



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