Hydrogenase in legume root nodule bacteroids: Occurrence and properties

Summary The hydrogenase found in Rhizobium bacteroids is compared with that found in Azotobacter and found, in all respects examined, to be similar. When three host species were inoculated with Rhizobium, strain 311, different amounts of hydrogenase activity were found in Pisum sativum and Vicia bengalensis while the enzyme was absent from nodules of Vicia faba. Of four different strains of Rhizobium examined only two strains possessed the hydrogenase when present in pea root nodules. The role of the hydrogenase in nitrogen fixation is discussed and it is tentatively concluded that the overall efficiency of the nitrogen fixation process is increased by its presence.