The Utilization of Nitrogen in Hydroxylamine and Oximes by Azotobacter vinelandii

Abstract

The Blom method for estimation of hydroxylamine is quantitative, but when applied to estimation of N in oximes after hydrolysis with organic acids, recovery is low and erratic. Estimation of oxime-N in the oximes of pyfuvic, oxalacetic and a-ketoglutaric acids by a microkjeldahl method gave better, but not completely, quantitative recoveries . However, the microkjeldahl method could be used for roughly quantitative estimations in metabolic experiments. In carefully controlled expts. made in both air and in H2-O2 mixtures (free of molecular N2) oxime-N in the oximes of pyruvic, oxalacetic and [alpha]-glutaric acid was not utilized by A. vinelandii. Under the same conditions, equivalent amounts of other combined forms of N, as the nitrate or ammonium compounds, were readily assimilated. The oximes did not prevent assimilation of molecular N2 in the air controls. Free hydroxylamine disappears from Burk''s N-free medium, probably because of decomposition. As long as the concentration of free hydroxylamine is greater than one [gamma]/ml., A. vinelandii will not grow; below this figure, hydroxylamine does not prevent assimilation of free or combined N, but itself is not utilized. It is concluded that the hydroxylamine and "oxirne" hypotheses for asymbiotic N-fixation should be rejected on the basis of these results.