In vivo interaction of trivalent chromium with yeast plasma membrane, as revealed by EPR spectroscopy

The in vivo effects of CrCl3 on an ergosterol-producing 33 erg(+) strain of the eukaryotic yeast Candida albicans, and on its ergosterol-deficient erg(-2) mutant, were studied by using electron paramagnetic resonance spectroscopy. A 5-doxylstearic acid spin probe was applied to label the membranes. The absence of ergosterol, an increased accumulation of Delta(8) sterols, a decreased fatty acid chainlength and a lower proportion of unsaturated fatty acids of the erg-2 mutant resulted in a higher membrane rigidity and an increased sensitivity to Cr(III) than those of the parental 33 erg(+) strain. Cr(III) significantly increased the fluidity of the spin labelled membranes, this being more pronounced for the erg(-2) mutant. The break in the slopes measured for the erg-2 mutant was decreased (Delta AT similar to 4 degrees C) from 17 to 13 degrees C. Cr(III) treatment for 10 h caused a loss of metabolites adsorbing at 260 nm: this loss was 40% for 33 erg(+) and 60% for erg(-2). This decriptification process might be the main cause of growth inhibition and cell killing by the impermeable Cr(III) ions. (C) 2000 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.