Relationship of proton motive force and the FSubs

Authors: Lilit Hakobyan Lilit Gabrielyan Armen Trchounian

Publish Date: 2012/06/12

Volume: 44, Issue: 4, Pages: 495-502

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Abstract

Rhodobacter sphaeroides MDC 6521 was able to produce biohydrogen H2 in anaerobic conditions under illumination In this study the effects of the hydrogenase inhibitor—diphenylene iodonium Ph2I and its solvent dimethylsulphoxide DMSO on growth characteristics and H2 production by R sphaeroides were investigated The results point out the concentration dependent DMSO effect in the presence of 10 mM DMSO H2 yield was ~6 fold lower than that of the control The bacterium was unable to produce H2 in the presence of Ph2I In order to examine the mediatory role of proton motive force ∆p or the F0F1ATPase in H2 production by R sphaeroides the effects of Ph2I 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 Ph2I decreased ∆ψ in concentrations of 20 μM and higher lower concentrations of Ph2I as DMSO had no valuable effect on ∆ψ The R sphaeroides membrane vesicles demonstrated significant ATPase activity sensitive to NN′dicyclohexylcarbodiimide The 10–20 μM Ph2I did not affect the ATPase activity whereas 40 μM Ph2I caused a marked inhibition ~2 fold in ATPase activity The obtained results provide novel evidence on the involvement of hydrogenase and the F0F1ATPase in H2 production by R sphaeroides Moreover these data indicate the role of hydrogenase and the F0F1ATPase in ∆p generation In addition DMSO might increase an interaction of nitrogenase with CO2 decreasing nitrogenase activity and affecting H2 production

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