RESPIRATORY ENZYME SYSTEMS IN SYMBIOTIC NITROGEN FIXATION I

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Abstract
Studies on the biochemistry of symbiotic nitrogen fixation (Wilson and Fred, 1937) indicate that oxidation reactions play a significant, though probably indirect, r6le in this process. A survey of the properties of the respiratory enzymes in species of the root-nodule bacteria (Rhizobium sp.), both when grown alone and with the proper host plant, appears necessary for progress on the problem of the mechanism of the reaction. Previous studies of the respiratory activities of the root-nodule bacteria (Georgi and Wilson, 1933; Neal and Walker, 1935, 1936; Thorne and Walker, 1935; Thorne, Neal and Walker, 1936; Walker, Anderson and Brown, 1934, a, b) were made primarily with growing cultures. Interpretation of the data is difficult since effects on growth are not readily differentiated from effects on respiration. The "resting cell" techniques eliminate many of the objections associated with studies made on growing cultures (Konishi and Tsuge, 1934). Resting cells, or more accurately, non-proliferating cells are washed suspensions of bacteria which are used as a source of enzymes for studies on bacterial metabolism. The enzyme is not separated from the cell but is "isolated" through use of specific substrates, inhibitors and other means. There is evidence (Quastel, 1928, 1932; Stephenson, 1930) that certain

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