Ultraviolet Light Inactivation and Photoreactivation of Blastocladiella emersonii

Some effects of ultraviolet light on Blastocladiella emersonii have been investigated. An action spectrum obtained at the zoospore stage of development suggests a large nucleic acid involvement in lethality. Zoospores damaged by short-wavelength UV light could be photoreactivated. This result strongly suggests that the critical lesions are pyrimidine dimers, most likely in DNA. Studies of the previously observed cyclical variations in UV sensitivity were extended. Germlings at one of the more resistant stages of the life cycle (1.5 hours of development) did not photoreactivate as rapidly nor to the same extent as did the cells at the very sensitive zoospore stage. These results may indicate a differential repair process or a difference in photoproducts at these stages. Acriflavin and dose fractionation experiments were inconclusive in verifying the existence of repair. Caffeine produced a small differential effect in lowering UV survival at different stages of the life cycle, but cells grown in the presen...