Influence of Silicon on Cobalt, Zinc, and Magnesium in Baker's Yeast, Saccharomyces cerevisiae

Abstract

Silicon (Si, as silicate) is involved in numerous important structure and function roles in a wide range of organisms, including man. Silicate availability influences metal concentrations within various cell and tissue types, but, as yet, clear mechanisms for such an influence have been discovered only within the diatoms and sponges. In this study, the influence of silicate on the intracellular accumulation of metals was investigated in baker's yeast (Saccharomyces cerevisiae). It was found that at concentrations up to 10 mM, silicate did not influence the growth rate of S. cerevisiae within a standard complete medium. However, an 11% growth inhibition was observed when silicate was present at 100 mM. Intracellular metal concentrations were investigated in yeast cultures grown without added silicate (-Si) or with the addition of 10 mM silicate (+Si). Decreased amounts of Co (52%), Mn (35%), and Fe (20%) were found within +Sigrown yeast cultures as compared to -Si-grown ones, whereas increased amounts of Mo (56%) and Mg (38%) were found. The amounts of Zn and K were apparently unaffected by the presence of silicon. +Si enhanced the yeast growth rate for low-Zn2+ medium, but it decreased the growth rate under conditions of a low Mg2+ medium and did not alter the growth rates in high Zn2+ and Co2+ media. +Si doubled the uptake rate of Co2+ but did not influence that of Zn2+. We propose that a possible explanation for these results is that polysilicate formation at the cell wall changes the cell wall binding capacity for metal ions. The toxicity of silicate was compared to germanium (Ge, as GeO2), a member of the same group of elements as Si (group 14). Hence, Si and Ge are chemically similar, but silicate starts to polymerize to oligomers above 5 mM, whereas Ge salts remain as monomers at such concentrations. Ge proved to be far more toxic to yeast than Si and no influence of Si on Ge toxicity was found. We propose that these results relate to differences in cellular uptake.

Modern Views on Desilicification: Biosilica and Abiotic Silica Dissolution in Natural and Artificial Environments

“…Current research ideas on silica toxicity and binding in the alveolar macrophage are reviewed and discussed by Hamilton et al 196 Probably silicate could play a role in organisms by its chemical interactions with metal ions. 28,29 Silicate-metal complexes could influence the availability of metals that are important for the organism (e.g., as an enzymatic cofactor). The effects on several biological processes could then be ascribed to the availability of important metal ions.…”

On the Beneficial Role of Silicon to Organisms: A Case Study on the Importance of Silicon Chemistry to Metal Accumulation in Yeast

“…Probably the adsorbed silicate has an influence on the cell's affinity for metal ions which is entirely dependant of chemistry. The results of earlier work [26] can be explained by this. The formation of a stable Mg-silicate complex on the cell wall could cause Mg 2+ ions to be "trapped" on the cell wall, reducing the availability of Mg 2+ ions for the cell.…”

“…Earlier it was found silicate interacts with several metals in the yeast cell [26]. In this experiment, it is investigated whether interaction of metals can be observed with the adsorbed silicate op the cell wall.…”

“…The study on Baker's yeast revealed that silicate affects metal concentrations and metal uptake rates in the cell, and that under certain conditions, the growth rate was affected. It was proposed that silicate adsorbed on the cell wall and influenced the metal availability for the cell by the formation of silicate-metal complexes [26].…”

Natural-resource potential of sarykum ecosystem and its use in viniculture

“…There are data that silicon is an obligatory compo nent of shells in yeast cells; it influences intracellular clusters of cobalt, magnesium, iron, and molybdenum (Ribero Gaion, Peino, 1971;Brasser, Krijer, Meerten, Wolterbeek, 2006).…”