Contribution of Delta pH and Delta E to photosynthesis of Chlamydomonas reinhardtii

The contribution of two components (Delta pH and DeltaE) of the proton moti ve force to photosynthesis of C. reinhardtii was studied. Valinomycin, a ph otophosphorylation uncoupler, decreased significantly the fast phase (relat ed mainly to the membrane electric potential) of millisecond delayed light emission (ms-DLE) of C. reinhardtii. Nigericin, another photo phosphorylati on uncoupler, decreased the slow phase (related mainly to the proton gradie nt) and partly also the fast phase of ms-DLE. Both valinomycin and nigerici n decreased the net ATP content and photosynthetic rate of C. reinhardtii, but the inhibition by nigericin was stronger than that by valinomycin. Henc e both components of the proton motive force contribute to photosynthesis a nd although the contribution of Delta pH is larger than that of DeltaE, the latter is not negligible in photosynthesis of C. reinhardtii.