Reactivation of photoinactivated single-stranded DNA bacteriophage phi X174 by UV-irradiated Escherichia coli cells.

Reactivation of single-stranded DNA phage, photodynamically inactivated in the presence of proflavine sulfate, by three isogenic Escherichia coli strains having different DNA repair capabilities has been studied. It was found that reactivation of photoinactivated phiX174 was possible only if the host cells were recombination proficient (recA(+)) and had been lightly irradiated with UV light prior to infection; the presence of the uvrA(+) gene was not essential. Only a small part of the proflavine-mediated photodynamic damage in phiX174 could be repaired in this fashion. Burst sizes of reactivated phages were, however, comparable to those of normal unirradiated phages.