Alternation of exo- and endotrophy during the mitotic cycle of the yeast cells.

Abstract

The utilization of the intracellular and extracellular sources of carbon and energy during the mitotic cycle of yeasts Saccharomyces cerevisiae, Kluyveromyces marxianus, Candida boidinii, Candida tropicalis has been studied. Increase in the consumption rate of carbon and energy sources and in the exogenous respiration rate at G1- and G2-phases of the mitotic cycle is shown. The rate of the endogenous respiration of the cells at these phases decreased. The hypothesis has been proposed that during the mitotic cycle of the yeast cell the regular alternation of exotrophy (the utilization of the extracellular carbon and energy sources by a cell) and endotrophy (the process of the utilization of the intracellular carbon and energy sources by a cell) occurs. It is possible to reveal the exotrophic cells by the cytological method which is based on the calculation of dead cells after incubation of the yeast suspension in amyl alcohol solution. This method has revealed that exotrophic and endotrophic processes do not predominate one over another but alternate at the mitotic cycle. Exotrophy and endotrophy are phase-specific processes. The G1- and G2-phases are exotrophic processes, phases S and M are endotrophic ones.