XXI ALAM
Resumo:1616-1


Poster (Painel)
1616-1Mercury toxicity to Saccharomyces cerevisiae
Autores:Jessica Paola Fuentes Rivera Navarro (ICB - USP - Biomedical Sciences Institute - University of São Paulo) ; Ana Clara Guerrini Schenberg (ICB - USP - Biomedical Sciences Institute - University of São Paulo) ; Carlos Alberto Brandt (INST. BUTANTAN - Instituto Butantan) ; Elisabete José Vicente (ICB - USP - Biomedical Sciences Institute - University of São Paulo)

Resumo

Large amounts of metals are released into the environment by anthropogenic activities. Among metals, mercury is recognized as a potent and widely distributed toxicant having the ability to accumulate at various levels of the food chain, besides being able to cross the placental and blood-brain barriers. The mercury toxicity mechanism involves the direct binding of its ions to thiol-containing compounds, such as enzymes and other proteins, thereby resulting in oxidative stress. Mercury induces oxidative stress in cells, leading to protein oxidation, lipid peroxidation, and DNA damage. In Saccharomyces cerevisiae, surprisingly, little is known about the mercury resistance mechanism, whereas there is considerable amount of knowledge about the resistance mechanisms towards copper and, to a lesser extent, cadmium. In the present work, a study of mercury toxicity to S. cerevisiae cells was carried out, measured by the loss of viability and of the functional groups responsible for Hg2+ binding to the yeast cell. The resistance to Hg2+ of two haploid (n) laboratorial strains (YPH252 and YPH274) and of one industrial strain PE-2 (2n used for bioethanol production), were evaluated. The yeast cells were grown in minimal medium SD-THUAL containing different concentrations of mercuric chloride (HgCl2), incubated at 28o C, for 72 h, and cell growth was determined by the Absorbance at 600 nm. All strains, haploid and diploid, showed similar high sensitivity to Hg2+ ions. In all cases, no growth was observed in 120 nM HgCl2. This result is consistent with previous results obtained when S. cerevisiae cells were exposed to another type of stress that occurs during ethanol production, and no correlation was observed between the sensitivity and ploidy of the strains (Bravim et al., 2010). Our results of Transmission Electron Microscopy (MET) confirmed that the mercury ions were associated with internal cell membrane structures inside the cytoplasm, after incubation of the cells in 1μM HgCl2, for 2h. In addition, the FT-IR results showed that the biomass has different functional groups where Hg2+ binding occurs. Probably, the high sensitivity of S. cerevisiae strains to the Hg2+ ions results from several sequential factors. Reference: Bravim et al. (2010). J. Ind. Microbiol. Biotechnol. 37: 1071-1079.


Palavras-chave:  Mercury, Oxidative stress, Toxicity, Saccharomyces cerevisiae