Bio-hydrogen production and the F0F1-ATPase activity of Rhodobacter sphaeroides: Effects of various heavy metal ions

Rhodobacter sphaeroides MDC 6521 isolated from Arzni mineral springs in Armenia is able to produce bio-hydrogen (H2) in anaerobic conditions upon illumination in the presence of various metal ions. The significant aspect in regulation of H2 production by these bacteria and its energetics is the requirement for F0F1-ATPase, the main membrane enzyme responsible for generation of proton motive force under anaerobic conditions. In order to determine the mediatory role of F0F1 in H2 production, the effects of various metal ions (Mn2+, Mg2+, Fe2+, Ni2+, and Mo6+) on N,N′-dicyclohexylcarbodiimide inhibited ATPase activity of R. sphaeroides membrane vesicles were investigated. These ions in appropriate concentrations considerably enhanced H2 production, which was not observed in the absence of Fe2+, indicate the requirement for Fe2+. The R. sphaeroides membrane vesicles demonstrated significant ATPase activity. In the absence of Fe2+ inhibition (∼80%) of ATPase activity was observed, which was increased by addition of metal ions. A higher ATPase activity was detected in the presence of Fe2+ (80 μM) and Mo6+ (16 μM). These results indicate a relationship between the F0F1-ATPase activity and H2 production that might be a significant pathway to provide novel evidence of a requirement for F0F1-ATPase in H2 production by R. sphaeroides.