Protection of normal, lysogenic, and pyocinogenic strains against ultraviolet radiation by bound acriflavine.

The presence of bound acriflavine protects bacteria against the lethal effects of ultraviolet (UV) light, presumably because pyrimidine dimer formation is inhibited. Although acriflavine present in plating medium usually results in reduced viable counts from irradiated bacteria, no enhancement of lethal effects is observed when acriflavine is added to irradiated bacteria left in suspending buffer for 45 min before plating. Acriflavine remaining bound to the deoxyribonucleic acid of irradiated bacteria at the time they are plated likewise does not affect their survival.