Comparisons of the effects of vacuum-uv and far-uv synchrotron radiation on dry yeast cells of different uv sensitivities.

Far-uv-sensitive (rad l/rad l) and wild-type cells of diploid Saccharomyces cerevisiae were irradiated in vacuum at 155, 170, 220, and 250 nm using synchrotron radiation (SR). Inactivation, gene conversion at leu l, and membrane damage as judged by methylene blue penetration were measured. Radiations of all these wavelengths killed dry yeast cells. In the vacuum uv, radiation at 155 and 170 nm induced membrane damage but not gene conversion, whereas far-uv radiation at 220 and 250 nm induced gene conversion but not membrane damage. The far-uv-sensitive strain showed no enhanced sensitivity to vacuum-uv radiation. These results indicate that damage to the cell membrane is considerably more important than to nuclear DNA for yeast cell inactivation by vacuum-uv radiation.