Resolution by high pressure liquid chromatography of intracellular and extracellular free amino acids of a nitrogen deficient marine diatom, Skeletonema costatum (Grev.) Cleve, pulsed with nitrate or ammonium

• Published in: Journal of experimental marine biology and ecology 1986-10, Vol.101 (1), p.101-117
• Main Authors: Haberstroh, Paul R., Ahmed, Saiyed I.
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Autoecology; Biological and medical sciences; Free amino acids; Fundamental and applied biological sciences. Psychology; Marine; Nitrogen; Plants and fungi; Skeletonema costatum
• ISSN: 0022-0981; 1879-1697
• DOI: 10.1016/0022-0981(86)90044-4

Nitrate and ammonium were added to nitrogen (N) deficient, batch cultures of Skeletonema costatum (Grev.) Cleve. The range of total internal free amino acids (IN FAAs) after N perturbations was 13.0–28.5 mM, while the total external FAAs (EX FAAs) varied from 3.9–17.5 μM. The total basic IN FAAs (and the total basic IN FAA N) predominated over the acidic and neutral IN FAAs (and acidic and neutral IN FAA N) after 50 h of N deficiency and after the N perturbations. Ornithine, a non-protein basic amino acid, was the most abundant individual IN FAA in N deficient cells, accounting for 43% of the total IN FAAs. All internal FAAs increased more quickly after the NH 4 + addition than after the NO 3 − addition. During the assimilation of either N addition, ornithine increased to a temporary peak concentration more rapidly than any other observed IN FAAs, and contributed up to 80% of the total IN FAA pool. After most of the respective N additions had been assimilated, and as free ornithine began to decrease, glutamine and glutamate increased to form a combined contribution of 30% of the total IN FAA pool. The increases of internal free glutamine and glutamate occurred more rapidly with the addition of NH 4 + than with NO 3 −, and these increases did not occur until the internal NH 4 + was depleted. The EX FAA did not undergo a distinct cycling in response to the NO 3 − or NH 4 + additions, as was observed with the IN FAAs. In contrast to the composition of the IN FAAs the most abundant EX FAAs were histidine (relatively sparse IN FAA), glutamate, aspartate, ornithine, and lysine.