Hydrogen Evolution from Soy-Bean Root Nodules

Wilson and Burris 1 reviewed the evidence implicating hydrogenase in biological nitrogen fixation and suggested two working hypotheses for the mechanism of nitrogen fixation which included the participation of hydrogenase. The relation between hydrogenase and nitrogen fixation was strengthened further when Kamen and Gest 2 discovered Rhodospirillum rubrum to be a nitrogen fixer and found that nitrogen, either as such or as ammonium, inhibited its photoproduction of hydrogen. Purified hydrogenase preparations from Clostridium pasteurianum have shown spectral changes when exposed to nitrogen relative to spectra under hydrogen, oxygen, nitric oxide or a vacuum 3 . Although the initial report 4 of hydrogenase in root-nodule bacteria was not verified by later, more extensive tests 5 with nodules and bacteria from nodules, Wilson 6 recently has reported that a preparation of disintegrated soy-bean nodules exhibited spectral shifts in the presence, as compared to the absence, of hydrogen, suggestive of the activity of a hydrogenase. The absence of a clear demonstration of hydrogenase in nodules often has been cited in discussion of the comparative biochemistry of nitrogen fixation as an irregularity. Evidence from the present communication removes this irregularity and establishes a further point of uniformity among nitrogen-fixing agents.