Selection of auxotrophic mutants in Saccharomyces cerebisiae by a snail enzyme digestion method.

Yeast cells in the stationary phase of growth are relatively resistant to snail enzyme digestion. This resistance was shown to decrease abruptly in the course of only 3-5 duplications, when stationary cells were allowed to grow in a fresh medium. The selective digestion of growing prototrophs from a mutagenized culture in minimal medium by snail enzyme was applied to increase the proportion of auxotrophs which remained relatively resistant.