[Nitrogenase and hydrogenase activities of the non-sulfur purple bacteria, Rhodopseudomonas spheroides and Rhodopseudomonas capsulata].

The greatest rate of acetylene reduction by Rhodopseudomonas spheroides and Rhodopseudomonas capsulata strains was found in the light in the presence of pyruvate, malate or lactate as well as, in the case of Rh. capsulata, in the presence of 10% H2. The activity of nitrogenase was higher in cells grown in the medium with malate than in cells cultivated in the medium with lactate. All the three strains of Rh. spheroides were characterized by a direct correlation between the rates of H2 photoproduction and C2H2 photoreduction. Such a correlation was not found for Rh. capsulata strains. This can be attributed to the fact that Rh. capsulata strains capable of effective H2 uptake utilize hydrogen evolved in the light in the presence of nitrogenase from organic substrates in order to reduce endogenous electron acceptors or acetylene, i.e. its recyclization takes place. In contrast to Rh. capsulata, Rh. spheroides cells exhibit a weaker hydrogenase activity measured in terms of hydrogen evolution and hydrogen uptake. The uptake of H2 is most active at the account of endogenous H-acceptors or in the presence of benzyl viologen and methylene blue but not methyl viologen.