Effects of Temperature and of Fatty Acid Substitutions on Colicin K Action

The temperature dependence of an early phase of colicin K action was studied. At temperatures of 10 C or lower, colicin K adsorbed to Escherichia coli cells, but its ability to cause physiological damage was greatly diminished. Cells treated with colicin K at 10 C exhibited nearly normal levels of beta-galactoside accumulation for that temperature, whereas a similar treatment at 27 C strongly reduced the levels of accumulation. Low temperatures also protracted the period during which viability could be restored to a colicin K-treated cell by a treatment with trypsin. Arrhenius plots for the progression of colicin K-treated E. coli cells from a trypsin-rescuable to an irrescuable state were biphasic in nature, with an increase in apparent activation energy occurring at temperatures below 21 C. Similar studies carried out with an E. coli unsaturated fatty acid auxotroph grown on structurally diverse unsaturated fatty acids revealed that the temperature profile for this phase of colicin K action is influenced by the fatty acid composition of the membrane phospholipids. The results are consistent with the interpretation that the action of colicin K on E. coli cells is sensitive to changes in the fluid properties of the membrane.