Intracellular appearance of nitrite and nitrate in nitrogen-starved cells ofAnkistrodesmus braunii

✍ Scribed by Hartmut Spiller; Elisabeth Dietsch; Erich Kessler

• Publisher: Springer-Verlag
• Year: 1976
• Tongue: English
• Weight: 704 KB
• Volume: 129
• Category: Article
• ISSN: 0032-0935
• DOI: 10.1007/bf00390025

✦ Synopsis

The occurrence of heterotrophic nitrification in nitrogen-starved cells of Ankistrodesmus braunii was confirmed. The levels of nitrate and nitrite were measured over a period of four weeks. The valid-•ty of quantitative determinations in the presence of highly active nitrate and nitrite reductases is discussed. Whereas free hydroxylamine as an intermediate could not be detected, increased hydroxylamine oxidase activity was found in nitrogen-starved cultures. Nitrite reductase and hydroxylamine oxidase can be assigned to particles by sucrose density gradient centrifugation. The possible involvement of microbodies, which were found to be present in Ankistrodesmus, in metabolic processes during nitrogen starvation is discussed. of either compound in Ankistrodesmus braunii, though assimilation of nitrate and nitrite as well as activity of nitrate reductase could be measured as early as 50 rain after nitrogen starvation. Since the concept of nitrification in a green alga is of some significance, we wish to evaluate the methods for the determination of intracellular nitrate and nitrite and to see if the generation of oxidized nitrogen can be followed over a period of time. Furthermore, we want to check whether the enzymes involved in the metabolism of inorganic nitrogen, i.e., nitrate reductase, nitrite reductase, and hydroxylamine oxidase, can be attributed to certain organelles. Finally, evidence is presented for the occurrence of microbodies, and the validity of their cytochemical staining in the diaminobenzidine reaction is questioned.