Free and bound magnesium in fungi and yeasts

Abstract

The content of total, bound and osmotically free magnesium was estimated in various fungi and in the yeastSaccharomyces cerevisiae. Total magnesium increases at lower growth rates ofEndomyces magnussi andPenicillium chrysogenum 140A as well as during the logarithmic stage of growth ofPenicillium chrysogenum Q-176. The binding of magnesium requires orthophosphate, decreasing during lack of external phosphate when the intracellular concentration of free magnesium rises. The fungi were found to contain a novel form of bound magnesium, a polymeric magnesium orthophosphate (PO_Mg), which appears to take part in the control of free magnesium level inPenicillium chrysogenum Q-176. The level of free magnesium is proportional to the growth rate ofEndomyces magnusii andPenicillium chrysogenum Q-176 and 140A. Total, as well as free, magnesium changes less than three-fold as external Mg concentration is changed 13,000-fold. The magnesium up against concentration gradients of 1∶25 to 1∶1300, the metal being distributed non-uniformation the cells ofSaccharomyces cerevisiae.