The influence of membrane fluidity on radiation induced changes in the DNA of E. coli K1060

E. coli K1060 a fatty acid auxotroph unable to synthesize unsaturated fatty acids was used to study the effect of membrane fluidity on survival and DNA damage after exposure to ionizing radiation. Oleic and elaidic acids were incorporated into the bacteria and the temperatures of irradiation chosen in order to give the maximum difference in survival between the "liquid crystal" and "gel" states. Maximum sensitization was achieved by cooling the bacteria for 5 min at ice temperature before irradiation. No sensitization was observed if cooling was after irradiation. Under non-nutrient conditions both oleic acid and elaidic acid grown bacteria were able to repair DNA strand breaks to the same extent. When irradiation was in nutrient conditions both bacteria at all temperatures of irradiation repaired DNA strand breaks equally well and to a greater extent than in non-nutrient suspension.