The effect of Cd2+ ions on the growth of Saccharomyces cerevisiae yeasts grown in a natural and a synthetic medium was studied. Two strains, B, i G,, were used. Both strains displayed high sensitivity to increased cadmium salt contents, particularly those grown in a synthetic medium. High concentrations of cadmium (> 50 pM) practically stopped the growth of the studied strains. The negative effect of cadmium ions was partly altered by adding zinc or calcium salts to the synthetic YM medium.
Ferric iron reductases activities have been occurred in 91% of investigated enterococci strains. Maximum activity occurred with coenzyme NADH as the reductant and the presence of cofactor FMN was necessary. Mg(II) ions has not stimulated reductases activity. Treatment of cells with proteolytic enzymes had not effect on iron reduction. The whole cells and cell fraction - cytoplasmic membrane and cytoplasm showed Fe(III) - reducing activity. The highest specific activity was associated with cytoplasm. The activity in cytoplasmic membrane was not related to iron concentration in the growth medium. In cytoplasm the activity was stimulated after growth in low-iron medium. Ferric iron reductases of enterococci characterized the broad substrate specificity. The iron in form of ferric ammonium citrate, lactoferrin and ferrioxamine B were the best iron sources for enterococcal ferric iron reductases.