Delayed plating recovery and protein synthesis in X-irradiated yeast

A study has been made of the effects of adding cycloheximide (an inhibitor of protein synthesis) to a holding suspension of X-irradiated Saccharomyces cerevisiae cells in phthalate buffer. Survival curves showed that the pronounced liquid-holding (LH) recovery shown by the cells was reduced by cycloheximide. The initial increase in survival after 1 day LH was not markedly changed by the addition of cycloheximide, but the survival after 4 days LH with cycloheximide was lower. LH itself had little effect on oxygen enhancement ratio, but the o.e.r. was significantly lower in the cycloheximide-treated cells. Liquid-holding recovery therefore requires protein synthesis for full expression, but the protein necessary must be present in sufficient amounts at the beginning of the holding period. (U.K.)