RADIOSENSITIZATION AND RADIOPROTECTION OF ESCHERICHIA-COLI BY ALCOHOLS

The survival of E. coli K12 strain AB1157 and the isogenic repair-defi cient mutant E. coli AB2480 (recA13, uvrA6) was measured after gamma-i rradiation in the presence of various alcohols as well as after incuba tion and subsequent removal of the alcohols before irradiation. Irradi ation in the presence of alcohols leads to the already known protectio n effect, which has been attributed to OH radical scavenging. However, it was not possible to explain the protection solely in terms of the reactivity of the OH radical with the various alcohols, because additi on of some of the alcohols did not yield the expected survival values. It was found that incubation with and subsequent removal of various a lcohols before irradiation led to radiosensitization. The degree of ra diosensitization increases with the hydrophobicity of the alcohol. In the case of glycerol no radiosensitization was observed. We can conclu de that alcohols protect predominantly by OH radical scavenging. The c omparatively small protection of cell survival by the more hydrophobic alcohols can be attributed to the sensitizing effect of these alcohol s.