HIGH-FREQUENCY PRODUCTION OF RESPIRATORY MUTANTS IN YEAST UNDER NUTRITIONAL DEFICIENCIES

Production of respiration-deficient mutants in unusually high frequencies up to 100% was observed when an originally stable, normal culture of yeast was grown in Schopfer's medium which is very simple and lacking in vitamines. The mutant production was significantly reversed, often to the minimal spontaneous level by addition of biotin, pantothenate, yeast extract and several amino acids, and also by substitution of the asparagine in Schoffer's medium with several nitrogenous nutrients. Such a production of respiratory mutants under nitritional deficiencies was found to be dependent largely upon the yeast species and strain. Two strains of Saccharomyces cerevisiae var. ellipsoideus readily produced 100% mutants. A few others produced close to 100% mutants after successive transfers, repeated 3 to 4 times, in Schopfer's medium. Yet other species remained normal even after repeated passages. Nutritional background conditions for hereditary maintenance of respiratory competence are discussed. © 1969.