The Effect of Various Metal Ions on Bio-hydrogen Production and F0F1-ATPase Activity of Rhodobacter Sphaeroides

Abstract

The important aspect in regulation of bio-hydrogen (H2) production by purple bacteria and its energetics is the requirement of the F0F1-ATPase, the main membrane mechanism generating proton motive force. Rhodobacter sphaeroides MDC 6521 (isolated from Arzni mineral springs in Armenia) is able to produce H2 in anaerobic conditions under illumination in the presence of various metal ions. In order to examine the mediatory role of the F0F1-ATPase 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. But the latter was not observed in the absence of Fe2+, indicating the requirement of Fe2+. The R. sphaeroides membrane vesicles demonstrated significant ATPase activity. The absence of Fe2+ caused to marked inhibition (~80 %) in ATPase activity. In the presence of Fe2+ (80 μM) and Mo6+ (16 μM) a higher ATPase activity was observed. These results indicate a relationship between H2 production and the F0F1-ATPase activity that might be an important pathway to regulate bacterial activity under anaerobic conditions and provide novel evidence on responsibility of F0F1 in H2 production by R. sphaeroides.