Participation of vacuoles in regulation of levels of K+, Mg2+ and orthophosphate ions in cytoplasm of the yeast Saccharomyces carlsbergensis

Abstract

Intracellular distributions of K+, Mg2+ and orthophosphate under various conditions of cultivation or incubation of the yeast Saccharomyces carlsbergensis were studied by differential extraction of ion pools. The decisive role of vacuolar compartmentation of ions in regulation of K+, Mg2+ and orthophosphate levels in the yeast cytoplasm was shown. The content of intracellular K+ and Mg2+ in yeast increased or decreased primarily depending on the increase or decrease in the vacuolar ion pool. The levels of K+ and Mg2+ in the cytoplasm were practically unchanged. Vacuoles were involved in regulation of Mn2+ concentration in the cytoplasm of the yeast S. carlsbergensis accumulating this ion in the presence of glucose. Alongside the vacuolar compartmentation, the chemical compartmentation, i. e. formation of bound Mg2+, Mn2+ and K+ was, evidently, also involved in the control of ion levels in the cytoplasm. The orthophosphate level in the yeast cytoplasm was regulated by its accumulation in vacuoles and biosynthesis of inorganic polyphosphates in these organelles. The biosynthesis of low-molecular weight polyphosphates occurred parallel to the accumulation of Mg2+ or Mn2+ in vacuoles, thus confirming the availability of the other mechanism for the transport of these ions through the tonoplast differing from the transport mechanism through the plasmalemma.