Mitochondrial changes accompanying acriflavine-induced petite mutation in saccharomyces fragilis

Unlike the highly fermentative bakers' yeast varieties of Saccharomyces, the faculatively anaerobic Saccharomyces fragilis does not exhibit glucose repression of respiration, or the Crabtree effect, nor of mitochondrial formation. Subjection of an actively fermenting culture of the latter species to acriflavine and replica plating on appropriate media resulted in a low yield of respiratory-deficient mutants. Electron microscopy of cells of a culture derived from one of the mutants revealed grossly modified mitochondria, as compared with those of its wild-type parent, although the numbers of this structure per cell were essentially unaffected. Glucose failed to repress mitochondrial formation in this mutant, as it does in both wild-type and respiratory-deficient mutants of S. cerevisiae, or bakers' yeasts, and, unlike these latter organisms, continuous feeding of low concentrations of glucose does not restore the formation of morphologically normal mitochondria.