The Utilization of Nitrate Nitrogen by the Azotobacter

Summary: Four types of utilization of nitrate nitrogen were observed with fourteen strains of the azotobacter. These were: (a) Those which utilize NO− 3 -N with no or only a short lag; three strains of Azotobacter vinelandii, a stock culture of A. chroococcum C-77, and seven strains of A. chroococcum freshly isolated from soil were in this group; (b) A single strain, a stock culture of A. chroococcum C-44, which uses NO− 3 -N only when conditions permit selection of a mutant capable of using this form of nitrogen; (c) A single strain, A. indicum 10, which uses NO− 3 -N very slowly in air and in which NO− 3-N accumulates; (d) A single strain, A. agile 4·4, which does not use NO− 3 -N. Certain other morphological and physiological differences between strains of A. vinelandii and the strain of A. agile 4·4 are pointed out which suggest that the question of the recognition of these strains as a single species be re-examined.