Cation (K~+, Mg~(2+), Ca~(2+)) exchange in Pb~(2+) accumulation by Saccharomyces cerevisiae

摘要

The relationship between Pb~(2+) accumulation and cation (K~+, Mg~(2+), Ca~(2+)) release in Saccharomyces cerevisiae was extensively investigated. As Pb~(2+) accumulation proceeded, the release of cellular metal ions such as K~+, Mg~(2+) and Ca~(2+) was concomitantly released within 24 h, thereafter Pb~(2+) penetrated into the inner cellular parts and consequently plasmolysis of the cell was observed by TEM analysis. Pb~(2+) accumulation process in S. cerevisiae after 24 h was metabolism-independent because of the absence of cell viability. As the cell storage time was prolonged, the released amount of K~+ was markedly increased, while the amount of accumulated Pb~(2+) was nearly constant regardless of cell storage time and the time required to reach an equilibrium state was shortened. The autoclaved cells had less Pb~(2+) accumulation capacity than the untreated cells, and the amounts of released K~+ and Mg~(2+) were very low due to the denaturation of cell surface and cell membrane.