Functioning of divalent alkaline metal on yeast multiplication in heavy metal contaminated soil

Abstract

Microbial parameters appear to be very useful in monitoring soil contamination by heavy metals. The toxic heavy metals cause serious threat to the environment, Nowadays, the most an important ecological problem is to correct the toxic effect of heavy metals in contaminated soils. In vitro, two strains of Saccharomy ces cerevisiae (NSS5099 and NSS7002) were tested in order to investigate their tolerance to heavy metals. The growth kinetics of two yeast strains in contaminated growth media by Cu²⁺, Pb²⁺, Cd²⁺ and Ni²⁺ were studied at 50 µM. The toxicity decreasing order of the investigated heavy metal salts on tested yeast strains was found to be Cu²⁺ > Pb²⁺ > Cd²⁺ > Ni²⁺. Ions of Cu²⁺, Pb²⁺ and Cd²⁺ at 350 µM and Ni²⁺ at 450 µM induced a decrease in the number of viable cells by 50% after 48 h incubation at 25°C. The addition of 50 mM Ca(HCO₃)₂, 75 mM MgSO , or 150 mM K SO in the growth broth medium before addition of 350 µM Cu²⁺, Pb²⁺ and Cd²⁺ or 450 µM Ni²⁺ shows a protective action against cell death and decreased the toxicity effect. The addition of alkaline metals reduced the effect of 350 and 450 µM of all investigated metals by 40%. The results obtained in the presented study exhibit the higher potentiality of S. cerevisiae strain NSS7002 than the strain NSS5099 to be used for decontamination of soil containing heavy metal ions. Further task is going to examine the range of metal bioaccumulation in the yeast cells and the ability of these strains to be environmental bioremediators.