HISTOCHEMICAL STUDIES OF MITOCHONDRIAL VARIATION DURING AEROBIC GROWTH OF RESPIRATION-NORMAL BAKER'S YEAST

Abstract

Histochemical localizations of cytochrome oxidase, succinic dehydrogenase, DPNH-tetrazolium reductase, and TPNH-tetrazolium reductase activities revealed at least two kinds of mitochondria in the intracellular population. The total chondriome in stationary phase cells contains about 45 mitochondria, all with cytochrome oxidase activity. But, only about 30 mitochondria per cell were active for dehydrogenase or reductases. The differences in mitochondrial enzyme activities persisted throughout the growth cycle, showing different numbers of active mitochondria and different rates of their increase and decrease for all four enzyme systems. Manometric data verified the differences between cytochrome oxidase and succinic dehydrogenase for the earlier phases of the growth cycle. In histochemical counts, zero values for all four enzymes occurred in late acceleration phase, but persisted into log phase only for the tetrazolium reductases. Both cytochrome oxidase- and succinic dehydrogenase-active mitochondria began to increase in numbers at the inception of log phase, but at very different rates. The demonstration of more than one kind of mitochondrion in the common nucleocytoplasmic system of a single cell was considered to be evidence of some measure of autonomous control of the mitochondrial phenotype.