Changes in intracellular amino acids and organic acids induced by nitrogen starvation and nitrate or ammonium resupply in the cyanobacterium Phormidium laminosum

• Published in: Planta Vol. 198; no. 4; pp. 526 - 531
• Main Authors: Tapia, M.I, Ochoa de Alda, J.A.G, Llama, M.J, Serra, J.L
• Format: Journal Article
• Language: English
• Published: Germany 01.04.1996
• Subjects: amino acids; ammonium compounds; biochemical pathways; biosynthesis; carbohydrates; carbon nitrogen ratio; chlorophyll; nitrates; nitrogen; nutrient deficiencies; nutrient reserves; organic acids and salts; Phormidium; proteins; Nitrate assimilation; Ammonium assimilation; Phormidium; Nitrogen starvation; Carbon-nitrogen interactions; Cyanobacteria
• ISSN: 0032-0935; 1432-2048
• DOI: 10.1007/BF00262638

In Phormidium laminosum cells, nitrogen starvation caused a decrease in the intracellular levels of all amino acids, except glutamate, and an increase in the total level of the analyzed organic acids. The addition of nitrate or ammonium to N-starved cells resulted in substantial increases in the pool size of most amino acids. Upon addition of ammonium the total level of organic acids diminished, whereas it increased upon addition of nitrate, after a transient decay during the first minutes. Nitrogen resupply stimulated amino acid synthesis, the effect being faster and higher when ammonium was assimilated. The data indicate that nitrate and ammonium assimilation induced an enhancement of carbon flow through the glycolytic and the tricarboxylic-acid pathways to amino acid biosynthesis, with a concurrent decrease in the carbohydrate reserves. The results suggest that the availability of carbon skeletons limited the rate of ammonium assimilation, whereas the availability of reducing equivalents limited the rate of nitrate assimilation.