[The age-dependent effect of copper ions on different strains of the wine yeast (Saccharomyces [corrected] cerevisiae var vini)]

Abstract

The chronological ageing of wine yeast strains isolated from natural populations and the resistance of cells of different age to copper ions have been studied. In total, 25 wine yeast strains derived from the "Tsolikauri" population of Sviri village (Imereti, West Georgia) were tested. The strains were transferred to the standard (control samples) and the copper sulphate-containing complete media and stored at 2 degrees C temperature. 10, 20 and 30 days after setting up the cultures their resistance to copper ions were examined. Methylene blue dye was used for identification of survived cells. Young strain cultures have revealed different resistance to copper ions. The strains under investigation may be conditionally divided into three morphs, such as: "sensitive" (capable of growing on 1-2 mM medium. 6 strains belong to this group), "mild" (grow on 3-4 mM medium--17 strains and "resistant" (can grow on 5 mM medium, includes 3 strains). The population was found to be polymorphic by the resistance to copper ions. The "sensitive" and "resistant" strains in spite of ageing (10 or 20 days after the onset of culturing) retain their resistance to copper ions, while the "mild" morphs exhibited some degree of variability. In the "aged" (30-day long) cultures strong inhibitory activity of copper ions was apparently observed. In contrast to the others, the resistance was sustained in the "resistant" morphs. The frequency of living cells was defined in the strains grown on the control and copper ion-containing substrates. Survived and died cells were counted. The strains belonged to the sensitive morphs contained high number of died cells--26-30%. The same index was rather low in the other morphs with no difference between them. Further ageing of the cultures (30 days and more) caused so sharp decrease in the liability of the strains, that they completely lose their resistance. Thus, the examined populations of the wine yeast were found to be polymorphic by their lifespan. They differ from each other by the speed of chronological ageing, that should be attributed to their genetic structure.