Relationship of proton motive force and the F(0)F          (1)-ATPase with bio-hydrogen production activity of Rhodobacter sphaeroides: effects of diphenylene iodonium, hydrogenase inhibitor, and its solvent dimethylsulphoxide.
Rhodobacter sphaeroides MDC 6521 was able to produce bio-hydrogen (H(2)) in anaerobic conditions under illumination. In this study the effects of the hydrogenase inhibitor-diphenylene iodonium (Ph(2)I) and its solvent dimethylsulphoxide (DMSO) on growth characteristics and H(2) production by R. sphaeroides were investigated. The results point out the concentration dependent DMSO effect: in the presence of 10 mM DMSO H(2) yield was ~6 fold lower than that of the control. The bacterium was unable to produce H(2) in the presence of Ph(2)I. In order to examine the mediatory role of proton motive force (∆p) or the F(0)F(1)-ATPase in H(2) production by R. sphaeroides, the effects of Ph(2)I and DMSO on ∆p and its components (membrane potential (∆ψ) and transmembrane pH gradient), and ATPase activity were determined. In these conditions ∆ψ was of -98 mV and the reversed ∆pH was +30 mV, resulting in ∆p of -68 mV. Ph(2)I decreased ∆ψ in concentrations of 20 μM and higher; lower concentrations of Ph(2)I as DMSO had no valuable effect on ∆ψ. The R. sphaeroides membrane vesicles demonstrated significant ATPase activity sensitive to N,N'-dicyclohexylcarbodiimide. The 10-20 μM Ph(2)I did not affect the ATPase activity, whereas 40 μM Ph(2)I caused a marked inhibition (~2 fold) in ATPase activity. The obtained results provide novel evidence on the involvement of hydrogenase and the F(0)F(1)-ATPase in H(2) production by R. sphaeroides. Moreover, these data indicate the role of hydrogenase and the F(0)F(1)-ATPase in ∆p generation. In addition, DMSO might increase an interaction of nitrogenase with CO(2), decreasing nitrogenase activity and affecting H(2) production.
Department of Biophysics, Yerevan State University, 0025, Yerevan, Armenia.
Lilit
L
Hakobyan
Lilit
L
Gabrielyan
Armen
A
Trchounian
D004121:Dimethyl Sulfoxide / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006859:Hydrogen / Q000378:metabolism*; D009861:Onium Compounds / Q000494:pharmacology*; D006180:Proton-Translocating ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism; D012242:Rhodobacter sphaeroides / Q000201:enzymology* / Q000254:growth & development; D012997:Solvents / Q000494:pharmacology*
D004791:Enzyme Inhibitors; D009861:Onium Compounds; D012997:Solvents; C007517:diphenyleneiodonium; D006859:Hydrogen; D006180:Proton-Translocating ATPases; D004121:Dimethyl Sulfoxide