초록
The aim of the present work was the study of comparative effects of Cu(II) and Ni(II) and their mixture on growth, redox potential, hydrogen (H<SUB>2</SUB>) yield and ATPase activity in phototrophic purple bacteria R. sphaeroides MDC6522 from Jermuk mineral spring in Armenia. It was ascertained, that Cu<SUP>2+</SUP> and Ni<SUP>2+</SUP> have different effects on bacterial specific growth rate: in the presence of 5μM Cu<SUP>2+</SUP> growth rate was ~3.2-fold lower in comparison with control (no addition), and increased ~1.5-fold in medium with 5μM Ni<SUP>2+</SUP>. These changes may be resulted by action of the ions on redox potential (E<SUB>h</SUB>). Low concentrations of Ni<SUP>2+</SUP> had an enhancing effect on the E<SUB>h</SUB> drop and H<SUB>2</SUB> production. The increase of concentration from 1 to 5μM enhanced the stimulatory effect of Ni<SUP>2+</SUP>. H<SUB>2</SUB> yield in R. sphaeroides (72h of growth) was enhanced ~3-fold with 5μM Ni<SUP>2+</SUP>, whereas in the presence of 5μM Cu<SUP>2+</SUP> H<SUB>2</SUB> yield was ~1.2 fold lower in comparison with control. Cu<SUP>2+</SUP>+Ni<SUP>2+</SUP> combinations effects were differed from the effect when ions used separately. When Cu<SUP>2+</SUP> and Ni<SUP>2+</SUP> were added together, the Ni<SUP>2+</SUP> stimulatory effect disappeared, which indicated that heavy metal ions mixture may have different action mechanisms. Moreover, N,N'-dicyclohexylcarbodiimide-sensitive ATPase activity of R. sphaeroides membrane vesicles has been increased in the presence of both ions, but in the presence of @?u<SUP>2+</SUP> the influence was feebly marked in comparison with Ni<SUP>2+</SUP>. The results suggest an interaction between these ions and the F<SUB>O</SUB>F<SUB>1</SUB>-ATPase. Thus, the results obtained point out discrimination between Cu<SUP>2+</SUP> and Ni<SUP>2+</SUP> and their combinations effects and reveal new regulatory pathways to enhance H<SUB>2</SUB> yield in R. sphaeroides.