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

The in vivo effects of CrCl(3) 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 (DeltaAT approximately 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.