Response of Saccharomyces cerevisiae to Heavy Element Stress: Lead vs. Uranium

Abstract

We have examined the responses of Saccharomyces cerevisiae in media containing Pb 2+ ions and compared it to those in media containing UO 2+ 2 ions to elucidate the stress effects of heavy elements. Cultivation of S. cerevisiae in a medium containing 1.0 × 10 −4 M Pb showed nearly the same growth as that in the control medium while growth was inhibited in the medium containing 1.0 × 10 −3 M Pb. Backscattering electron image analyses of thin sections of cells showed that Pb had accumulated inside the cells. These results were different from those for UO 2+ 2 ions obtained in the previous study, where 1.0 × 10 −4 M U inhibited the growth of S. cerevisiae, and UO 2+ 2 ions were sorbed on the cell surface. Two-dimensional (2D) gel electrophoresis analysis of the proteins extracted from the S. cerevisiae exposed to Pb 2+ ions showed that several specific protein spots were expressed after cultivation with Pb, that did not appear in the control medium. The isoelectric point in the gel strip and molecular sizes of the specific proteins expressed by Pb 2+ were different from those by UO 2+ 2 . Our results suggest that Pb 2+ more weakly inhibits the growth of S. cerevisiae than UO 2+ 2 , and produces different stresses in S. cerevisiae than UO 2+ 2 .