Preliminary ESR study of Mn(II) retention by the yeast Saccharomyces

Manganese(II) retention by yeast cells was investigated in the absence of any energy source in the medium. Only a small fraction of the cations retained (2.7 to 9%) was bound by the cell wall; the binding sites were negatively charged groups like phosphodiesters in the phosphomannan and carboxylates in the proteins. ESR spectra of the cations, which entered the cell, indicated that they could be complexed by polyelectrolytes or precipitated with orthophosphate to form MnHPO4(crystal). In both cases, the concentration of free Mn2+ remained low. The entry of cations was thus driven by the concentration gradient, and no metabolic energy was therefore required in our experimental conditions.