OXYGEN EFFECT IN SURVIVAL OF Dictyostelium discoideum TREATED WITH NEAR ULTRAVIOLET RADIATION

Fluence‐response survival curves have been measured for the cellular slime mold Dictyostelium discoideum exposed to near ultraviolet radiation. Data were obtained for a wild type strain and three UV‐sensitive mutant strains in exponential growth phase. Fluences for 10% survival (F10) are about 1 MJ m−2 for cells irradiated in saline solution saturated with nitrogen. When air is bubbled through the saline, the Fm values are only one third as large. Strain HPS50, which is the strain most sensitive to gamma radiation and to 254 nm UV, also exhibits the greatest sensitivity to near UV. However, the difference in sensitivity to near UV between wild type and mutant strains is small compared to other physical and chemical agents known to damage DNA.