When the extent of liquid holding recovery (LHR) was measured as a function of the temperature at the time of liquid holding and the Arrhenius plot was made, two distinctive phases for the LHR were demonstrated in UV-irradiated RecA − derivative of E. coli ole28E 1, which are unable to synthesize and degrade unsaturated fatty acids. The inflection temperatures were 17–18°C, 23–24°C and 28–30°C for linoleate-, oleate- and elaidate-grown cells, respectively. These temperatures well corresponded to the phase transition temperatures of the cell membrane supplemented with the fatty acid. It is therefore concluded that at least a component involved in in vivo excision repair in E. coli is associated with cell membrane.