ISSN:
1399-3054
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
Over a period of several days, rhythmic changes in extracellular NH+4 concentration take place in cultures of the cyanobacterium Microcystis firma (Bré et Lenorm.) Schmidle, strain Gromov/St. Petersb. 398, under conditions of restricted CO2 supply and light/dark alternation. The changes are enhanced by nitrate supply. Among the various processes generating intracellular NH+4 (NH44 uptake, NO−3 reduction, protein and amino acid degradation, photorespiration), NO−3 reduction appears as the one most important. This can be concluded from experiments with and without nitrate and/or ammonium in the medium. In the presence of saturating CO2, continuous light, or continuous darkness, rhythmic NH+44 oscillations are not induced. Studies of the incorporation of NH+4 nitrogen by in vivo 15N-NMR show that if CO2 is supplied, 15N is accumulated in several components with the following time course: in the first hour in Gln (δ), in the second hour in the α-amino groups of most nonbranched amino acids, in the third hour in γ-aminobutyric acid (GABA), Orn (δ) and Lys (ε), and in the sixth hour in Ala. Carbon limitation, however, results in accumulation of label in the amide nitrogen of glutamine only.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1399-3054.1993.tb05230.x
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