PRODUCTION OF PETITE MUTANTS OF SACCHAROMYCES CEREVISIAE BY PATULIN

Patulin, an antibiotic produced by several species of Aspergillus and Penicillium, is carcinogenic in rats. The activity of this compound was investigated in an extrachromosomal mutation system of a haploid strain of Saccharomyces cerevisiae. The yeast cells were exposed to several concentrations of patulin for varying periods of time and the colonies produced by the survivors of such treatment were tested for their ability to reduce 2,3.5-triphenyltetrazolium chloride to its red formazan. In this manner, mutation from wild type to petite can be observed; petite colonies cannot reduce the test compound and therefore remain white. Yeast cells in exponential phase of growth were more sensitive to the toxic and mutagenic effects of patulin than were cells in stationary phase of growth. Exposure to 50 μ, per ml. of patulin for 3 hours during exponential phase resulted in a mutation frequency of 60 to 80% with 1% survival whereas similar treatment of stationary phase cells resulted in a mutation frequency of approximately 10% with 80% survival. Toxicity, as measured by loss of viability, was apparent at the same concentration range of patulin which produced mutation. © 1969, American Chemical Society. All rights reserved.