ACRIFLAVINE INDUCTION OF DIFFERENT KINDS OF "PETITE" MITOCHONDRIAL POPULATIONS IN SACCHAROMYCES CEREVISIAE.

Avers, Charlotte J. (Rutgers, The State University, New Brunswick, N. J.), Cynthia R. Pfeffer, and Martha W. Rancourt. Acriflavine induction of different kinds of "petite" mitochondrial populations in Saccharomyces cerevisiae. J. Bacteriol. 90:481-494. 1965.-Mutant frequencies induced by 1 or 2 hr in 16 and 64 mug/ml of acriflavine were significantly higher during acceleration and log-phase exposures than during lag or stationary phases. From these induced petites, 59 colonies were selected at random and established in pure culture. All strains were analyzed histochemically for mitochondrial cytochrome oxidase and succinic dehydrogenase (SDH) reactions. On the basis of counts of stained mitochondria per cell obtained by light microscopy, four different cell phenotypes were recognized among the mutant strains: (i) reduced cytochrome oxidase, wild-type SDH; (ii) reduced cytochrome oxidase, high SDH; (iii) absent cytochrome oxidase, high SDH; and (iv) absent cytochrome oxidase, wild-type SDH. The last group was the most common, characterizing 43 of the 59 strains. Electron microscopy showed differences in mitochondrial ultrastructure for the various cell phenotype classes. Electron histochemical localizations showed cytochrome oxidase reaction product only on mitochondrial membranes of respiration-competent cells. Both reactive and unreactive mitochondria occurred in the same cell in mutants with partial respiratory competence. Different mitochondrial subpopulation mixtures characterized the mutant strains, many of which had at least two kinds of respiratory-competent types per chondriome. The diverse chondriomes comprised a stable feature of the mutants, since they have been maintained unchanged during serial transfer for more than 1 year in culture. Together with earlier reports of at least two kinds of mitochondria in wild-type cells, the evidence indicated that mitochondria were capable of regulating some portion of their phenotype. The recognition of mitochondrial phenotypes was proposed as an initial step in a formal analysis of organelle heredity.