The utilization of nitrate nitrogen by the Azotobacter.

Four types of utilization of nitrate nitrogen were observed with fourteen strains of the azotobacter. These were: (a) Those which utilize NO;-N with no or only a short lag; three strains of Azotobacter winelandii, a stock culture of A. chroococcum C-77, and seven strains of A. chrmoccum freshly isolated from soil were in this group; (b) A single strain, a stock culture of A. chroococcum C-44, which uses NO;-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;-N very slowly in air and in which NO;-N accumulates ; (d) A single strain, A. agile 4.4, which does not use NO;-N. Certain other morphological and physiological differences between strains of A. winelandii and the strain of A. agile 4-41 are pointed out which suggest that the question of the recognition of these strains as a single species be re-examined.