Ultraviolet Radiation Sensitivity of White Mutants and Red Wild-Type Serratia marcescens

White mutants of Serratia marcescens, which do not produce the nonessential pigment prodigiosin, were found to be more resistant to killing by ultraviolet light (UV) than the red-wild type. Pigment induction in a white mutant, which sensitizes to gamma rays, does not change this mutant's UV resistance. Therefore, prodigiosin does not appear to sensitize to UV killing in these strains. Possible differences in UV sensitivity due to UV-induced lysis and filament formation were checked, but not observed. Post-UV plating of red and white Serratia on caffeine and acriflavin was found to decrease the survival for both strains, reflecting the probable existence of repair.