Hydrazine and biological nitrogen fixation

Abstract

The disappearance of hydrazine from washed suspensions of Azotobacter vinelandii was stimulated by the addition of potassium cyanide and acetaldehyde to the reaction mixture and was inhibited by the addition of ammonium sulfate. Most of the hydrazine which disappeared in this reaction could be recovered by acid hydrolysis of the organic azines which were formed; N 2 and ammonia- were minor products of this reaction. Hydrazine and α-ketoglutarate combine to form 3,4-dihydropyridazinone-5-carboxylic acid in very dilute buffered solutions near neutrality without the mediation of biological agents. The organic azines formed in the biologically mediated disappearance of hydrazine appeared to be identical to those formed in the chemical reaction between α-ketoglutarate and hydrazine. These azines were present in A. vinelandii cells grown on N 2 and in the nodules of field-grown soybeans. The fractions from paper chromatograms carrying the azines contained a higher relative and absolute atom % 15N excess than ammonia or glutamic acid when the azotobacter cells were exposed to 15N 2, but not when they were supplied 15NH 4 +. The implications of these results for the mechanism of biological N 2 fixation are discussed.