Ammonia Assimilation and Excretion in an Asymbiotic Strain of Anabaena azollae from Azolla filiculoides Lam.

William J. Zimmerman, Sammy Boussiba

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One independent, asymbiotic strain of Anabaena azollae isolated irom Azolla filiculoides Lam. was examined with respect to ammonia «uptake», assimilation, and excretion. Extracellular release of ammonia was initiated by adding L-methionine-D,L-sulfoximine (MSX). NH3-grown cells removed newly added ammonium from the medium faster (25.2 to 19.7nmol min−1 mg−1 protein), liberated ammonia more slowly (0.33 to 0.63 μmol h−1 mg−1 protein), and possessed lower glutamine synthetase (GS) transferase activity (55%) than the N2-grown cells. GS was always still partially active (20–40 % of uninhibited control) in A. azollae when excretion commenced. Uninhibited GS activity was lower than that of Anabaena sp. 7120. No optimum was observed between pH 5 and 9 for ammonia movement into or out of cells of A. azollae.

Original languageEnglish
Pages (from-to)443-450
Number of pages8
JournalJournal of Plant Physiology
Issue number5
StatePublished - 1 Jan 1987


  • Anabaena azollae
  • GS
  • Glutamine synthetase
  • L-methionine-D,L-sulfoximine
  • MSX
  • ammonia excretion
  • ammonia uptake
  • cyanobacteria
  • glutamate synthase
  • glutamine synthetase
  • symbiosis


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