Toxicity of organic and inorganic mercury to Saccharomyces cerevisiae

In this study the effect if six different forms of mercury on the growth of the yeast Saccharomyces cerevisiae is presented. Five kinds of strains of S. cerevisiae were used. They were a wild type, a mercury-resistant type, a nd three mutants: mutation repair-deficient mutant, excision repair-deficie nt mutant, and recombination repair-deficient mutant. In terms of EC,, towa rd the mild-type strain, the toxicity order for the inorganic forms was Hg( NO3)(2)>HgSO4>HgCl2. Monovalent nitrate mercury Hg(NO3)(2) was more toxic t han bivalent Hg(NO3)(2). The toxicity of organic mercury CH3HgCl on cell gr owth was two orders of magnitude higher than that of inorganic HgCl2. Betwe en the two organic forms, CH3HgCl mas more toxic than CH3HgOH. The survival rate in the presence of a certain concentration of CH3HgCl was about one-h undredth of the survival in presence of the same concentration of HgCl2. On the other hand, the concentration of CH3HgCl in the cell was about 170 tim es that of HgCl2. The addition of chelating agents, EDTA and methyl-penicil lamine, to the medium did not reduce the toxicity of mercury. Among the thr ee mutants tested, the one deficient in recombination repair systems was th e most sensitive to mercury, (C) 1999 Academic Press.