Cadmium accumulation and its effects on intracellular ion pools in a brewing strain of Saccharomyces cerevisiae

The presence of glucose resulted in a two- to three-fold increase in levels of Cd2+ accumulated by Saccharomyces cerevisiae after 5 h compared with th ose observed in the absence of glucose. However, time-dependent Cd2+ uptake continued in the absence of glucose over 5 h, resulting in an appreciable increase in cellular Cd2+ levels. Substantial K+ efflux but little Mg2+ and negligible Ca2+ release was observed. Cell fractionation revealed that the bulk of intracellular Cd2+ was located in the vacuolar (25%) and bound (60 %) fractions. Accumulation of Cd2+ ions Impacted most noticeably on K+ rath er than Mg2+ levels in intracellular compartments. Cytoplasmic and particul arly vacuolar K+ levels decreased as Cd2+ sequestration continued resulting in increased extracellular levels. In contrast, corresponding intracellula r Mg2+ pools were only modestly affected with a slight Increase and decreas e observed in the cytoplasmic and vacuolar fractions respectively, However, levels of bound Mg2+ decreased in response to continued Cd2+ accumulation.