Photo-reactivation of gamma-radiation damage in Escherichia coli as evidence for the nature of the oxygen-enhancement effect.

The enhancement of gamma-radiation-induced damage in bacteria by the presence of oxygen during irradiation has been attributed to changes in the rate of formation, or alternatively in the repair, of single-strand breaks. This paper presents data which support the hypothesis that the observed effect of oxygen of modifying viability after irradiation is in part associated with lesions other than DNA single-strand breaks. In particular, the influence of oxygen during gamma-irradiation on the subsequent efficiency of photo-reactivation and excision repair is used to demonstrate that oxygen enhancement is due to a reduction in the excision repair of non-photo-reactivable damage.