Fixed nitrogen assimilation

The phototrophs that assimilate fixed nitrogen preferentially utilize ammonium over nitrate or nitrite. (Some phototrophs assimilate DON, such as urea, to meet their nitrogen needs, and, hence, are not strict autotrophs.) Ammonia is fevored over the more oxidized forms of DIN as less redox energy is required to incorporate its nitrogen into biomolecules, primarily amino acids and the nucleotide bases. 

Was this youT answer Plants use nitrogen to build proteins. Nitrogen-fixing plants assimilate a lot of nitrogen and so produce proteins in large quantities. 

Figure 24-1 The nitrogen cycle. Conversion of N2 (oxidation state 0) to NH4+ by nitrogen-fixing bacteria, assimilation of NH4+ by other organisms, decay of organic matter, oxidation of NH4+ by the nitrifying bacteria Nitrosomas and Nitro-bacter, reduction of N03 and N02 back to NH4+, and release of nitrogen as N2 by denitrifying bacteria are all part of this complex cycle.1...

From a quantitative perspective, the most important process of the fixed nitrogen cycle in the ocean is the assimilation of NOJ and NH4 into organic nitrogen in the... 

Here we assume a source of fixed nitrogen in the form of nitrate. Alternatively, diazotrophs can fix their own nitrogen, reducing N2 gas to the level of ammonium in order to be assimilated for protein synthesis. Ammonium may be oxidized by nitrifying bacteria to produce nitrite and nitrate and consuming molecular oxygen ... 

Nitrate reduction studies have focused overwhelmingly on denitrification at the expense of other NO sinks such as dissimulatory NO reduction to NH4 (also known as DNRA or nitrate ammonification). The ecological implications of reducing NOJ to NH4, versus N2 are vastly different because NH4 is more readily retained in the ecosystem, and it is a form that is readily assimilated by biota. Thus, DNRA contributes to eutrophication by reducing the quantity of fixed nitrogen that is returned to the atmosphere as N2. 

R516 L. Rosendahl, A. Rudbeck, A. M. Scharff and P. Mouritzen, Assimilation of Fixed Nitrogen Studied by Membrane Vesicle Transport and in Vivo N-NMR Spectroscopy in Pea , Curr. Plant Set Biotechnol Agric., 2000, 38, 351... 

Assimilation of Recently Fixed Nitrogen in Soybean Nodules. 

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