Use of a fatty acid auxotroph to study the role of membrane patty acid composition on the pressure resistance of Escherichia coli

E. coli K1060, a mutant defective in the synthesis and degradation of unsaturated fatty acids, was used to obtain membranes of different fatty acid composition without altering other growth parameters. The pressure resistance of the cells varied according to the different fatty acid supplement used in the growth medium. Cells grown on elaidic acid were the least pressure resistant in exponential phase and the most resistant in stationary phase. The fluidity of the membrane, as measured by differential scanning calorimetry of stationary-phase cell lipids, showed a secondary peak at high temperature (51.9 degrees C) for cells grown on elaidic acid. Cells with a more rigid membrane were more sensitive to pressure in exponential phase and more resistant in stationary phase confirming the results previously obtained with cells grown at different temperatures.