Lack of additive effect in mutagenesis of E. coli by UV-light and ethylene oxide.

The interaction of UV-irradiation and ethylene oxide (EtO) on forward mutation frequencies in the lacI gene of E. coli strains 3835 and 3951 and on the frequency of leu+ revertants in E. coli WU36-10-89 were studied. Pre-exposure to low doses of UV-light with the following treatment by low and intermediate doses of EtO showed lack of additive effect in the mutagenic response in all strains studied. The number of mutants actually obtained in the respective experiments was much lower than the additive model predicted.