ACUTE TOXICITY OF 16 WATER-SOLUBLE CHEMICALS TO THE FUNGUS GEOTRICHUM-CANDIDUM MEASURED BY REDUCTION IN GLUCOSE-UPTAKE

A method for the estimation of chemical inhibition of glucose uptake by the fungus Geotrichum candidum was developed. Inhibition of glucose uptake was measured in cultures of germinated spores of G. candidum treated for 4 hr with 16 different water-soluble chemicals. The assay was performed in microtitre trays. Under control conditions the fungus had a glucose uptake of 200-230 mu g/ml (noninhibited cultures). The glucose assay was linear up to 600 mu g glucose/ml with a detection limit of 12.2 mu g glucose/ml. All of the chemicals inhibited glucose uptake. IC50 values were extrapolated from dose-response curves. The IC50 values ranged from 0.006 (mercuric chloride) to 1500 mM (methanol). A highly significant correlation between IC50 values in the fungal test and human lethal blood concentrations (r = 0.83) was found for the 16 chemicals. A significant correlation was also found between IC50 from the assay with the fungus and the minimal inhibition concentration in bacteria (r = 0.78) and IC50 values obtained with [H-3]proline incorporation in cell cultures (r = 0.87).