The Effects of Exogenous Amino Acids on Growth and Nitrogenase Activity in the Cyanobacterium Anabaena cylindrica PCC 7122

Summary: Growth and nitrogenase activity were followed in batch cultures of Anabaena cylindrica PCC 7122 supplemented with a range of protein amino acids and urea at concentrations of 1 and 10 mm. Alanine, arginine, asparagine, aspartate, glutamate, glutamine and serine caused reductions in nitrogenase activity and showed evidence of acting as sources of nitrogen. Suppression of nitrogenase by other amino acids was accompanied by reduced growth. A number of amino acids appeared to be toxic at high concentrations. Cysteine and histidine were toxic at low concentrations.