Is the ubiquinone pool in the respiratory chain of the bacterium Paracoccus denitrificans really unhomogeneous?

We have established the participation of a mobile redox pool in the respiratory chain of anaerobically grown bacterium Paracoccus denitrificans. In testing the kinetical homogeneity of the pool it was found that the ratio of fluxes of electron transport toward the terminal acceptors oxygen and nitrate was coincident for the respiratory substrates NADH and succinate; this provides evidence against the preferential link of one dehydrogenase with a distinct terminal enzyme through the separate pool of ubiquinone. The deviation from the expected behavior observed in comparing the titration of NADH oxidase and succinate oxidase with respiratory inhibitors such as mucidin (inhibitor in the bc1 region) or cyanide can be accounted for by the activation of succinate dehydrogenase upon the increase in the reduced state of respiratory components during the titration.