Liquid holding recovery and photoreactivation of UV-induced damage inStreptococcus lactis

Summary Repair of ultraviolet-light-induced DNA damage inStreptococcus lactis has been examined. The wild-type strain and its derivative Lac^– possess a dark repair system (maximal increase in survival of 4-fold). Enzymatic photoreactivation exists in the two strains but a weaker photoreactivability was found in the Lac^– derivative (4 and 2-fold, respectively). Concomitant reduction of UV-induced mutagenesis (Rif^r marker) was also studied during these two repair phenomena. The absence of dark repair after saturation of photoreactivation suggests that photoreactivation is much more efficient with pyrimidine dimers as substrate.