Physiological and biochemical studies on nitrogen fixing blue-green algae

Summary The nature of the nitrogenous products formed in the cells and culture solutions of a nitrogen fixing strain of Nostoc commune was investigated. This organism was able to fix 5.4 mg nitrogen/100 mg dry algal cells. 13% of this cellular nitrogen was present in the soluble form. The assay of the different fractions of this soluble nitrogen was also made. Aspartic acid, glutamic acid and alanine were the only amino acids present in the free form. The extracellular nitrogen amounted to 30% of the total fixed nitrogen. The different fractions of this nitrogen were also assayed. Glutamic acid and aspartic acid were the only free amino acids in the culture solution. The importance of these two acids in the pathway of the fixation mechanism was discussed.