Repair of damage induced by a monofunctional alkylating agent in a transformable, ultraviolet-sensitive strain of Bacillus subtilis

An ultraviolet-sensitive, transformable strain of Bacillus subtilis (uvr−) was unable to carry out host cell reactivation of the virulent bacteriophage SP01, and Whole uvr+ cells recovered from ultraviolet-induced damage, as determined by an increase in extractable transforming activity during a period of incubation in which net DNA synthesis did not occur.

Abstract

An ultraviolet-sensitive, transformable strain of Bacillus subtilis (uvr−) was unable to carry out host cell reactivation of the virulent bacteriophage SP01. The ratio of the slopes (kuvr-/kuvr+) of the ultraviolet-inactivation curves was 6 to 8 for cells or for whole phage, and 2 to 3 for indole+ transforming DNA or for SPOl phage DNA measured in a transforming system. Whole phage inactivated with nitrogen mustard showed greater survival on uvr+ cells than on uvr− ; there was no such difference for whole phage inactivated with methyl methanesulfonate. Whole uvr+ cells recovered from ultraviolet-induced damage, as determined by an increase in extractable transforming activity during a period of incubation in which net DNA synthesis did not occur. Uvr− cells were unable to recover from ultraviolet-induced damage but they did recover from methyl methanesulfonate-induced damage in similar experiments. Density-labeled [2H15N] methyl methanesulfonate-treated uvr+ cells incubated in [1H14N]medium containing [3H]thymidine showed a threefold increase in extractable transforming activity, with no formation of new DNA molecules as determined by pyenometric analysis. The repair of damage induced by ultraviolet irradiation differs by at least one step from the repair of damage induced by methyl methanesulphonate.