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 spectros copy. 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 fat ty 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(+) strai n. Cr(III) significantly increased the fluidity of the spin labelled membra nes, this being more pronounced for the erg(-2) mutant. The break in the sl opes measured for the erg-2 mutant was decreased (Delta AT similar to 4 deg rees C) from 17 to 13 degrees C. Cr(III) treatment for 10 h caused a loss o f 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 growt h inhibition and cell killing by the impermeable Cr(III) ions. (C) 2000 Fed eration of European Microbiological Societies. Published by Elsevier Scienc e B.V. All rights reserved.