A new method for mutant selection in Saccharomyces cerevisiae.

A new method for the selection of auxotrophic, antibiotic- and temperature=sensitivemutants in Saccharomyces cerevisiae is reported. The technique is based upon the observation that certain fatty acid auxotrophs of yeast die when deprived of fatty acid only under conditions supporting growth. When macromolecular synthesis is blocked, the fattyacid-starved cells survive. By appropriate manipulation of a fatty acid-requiring strain enrichment as great as 75-fold was achieved for certain classes of auxotrophic mutants. An enrichment of approximately 100-fold is possible for some antibiotic-sensitive mutants. Selection for temperature-sensitive mutants, however, resulted in less than a 2-fold increase in the frequency of such mutants, probably because of the heterogeneity ofthis mutant category. It is likely that only that fraction of temperature-sensitivemutations which rapidly and reversibly blocks macromolecular synthesis is selected by this technique.