Reduction of vanadate to vanadyl by a strain of Saccharomyces cerevisiae

Three strains of Saccharomyces cerevisiae, SC-1, DBVPG 6173 and DBVPG 6037, were studied for vanadate resistance in complex Sabouraud medium since they did not thrive in different minimal media (yeast nitrogen base with and without Amino acids). The strain SC-1 was resistant up to 16 mM of vanadate, whereas the strains DBVPG 6173 and DBVPG 6037 were inhibited by 8 mM and 4 mM vanadate, respectively. The vanadate resistance in strain SC-1 was constitutive and due to the reduction of this oxyanion to vanadyl, which was detected by EPR spectroscopy and visible spectroscopy. The transformation of vanadate to vanadyl took place during the exponential growth phase; 10 mM of vanadate was reduced to vanadyl outside the cells since the oxyanion was not detected in the cell biomass and only a negligible concentration of vanadyl (25 nmoles mg-1 cells dry weight) was found in the biomass. The other two vanadate-sensitive yeast strains only accumulated vanadate and did not reduce the oxyanion to vanadyl.