Nitrogen uptake bacterial

Tungaraza, C., Brion, N., Rousseau, V., Baeyens, W., and Goeyens, L. (2003a). Influence of bacterial activities on nitrogen uptake rates determined by the application of antibiotics. Oceanologia 45, 473—489. 

Ureases [27] Niai)-Niai) Hydrolysis of urea Treatment of bacterial infections, regulation of nitrogen uptake in plants... 

CoUier, J. L., Brahamsha, B., and Palenik, B. (1999). The marine cyanobacterium Synechococcus sp. WH7805 requires urease (urea amidohydrolase, EC 3.5.1.5) to utilize urea as a nitrogen source molecular-genetic and biochemical analysis of the enzyme. Microbiol.—U.K. 145, 447—459. CoUos, Y. (1998). Covariation of ammonium and nitrate uptake in several marine areas Calculation artefact or indication of bacterial uptake Preliminary results from a review of 76 studies. In Integrated Marine System Analysis. Dehairs, F., Elskens, M., and Goeyens, L. (eds.). Vrije Universiteit, Brussel, pp. 121—138. 

The loss terms in N-cycle models that transform particulate and dissolved organic nitrogen into other forms can include a variety of processes (e.g., phytoplankton exudation, zooplankton grazing, sloppy feeding, phytoplankton and zooplankton mortality, bacterial remineralization, etc.). Different models may differ substantially in terms of which of these are included and their formulation (Christian and Anderson, 2002). Many N-cycle models now include significant phytoplankton exudation loss terms. This is often parameterized by simply specifying that some fixed fraction of the DIN uptake by phytoplankton is shunted directly to the DON pool (e.g., Anderson and Williams, 1998). Sloppy feeding by zooplankton can be similarly accounted for. Many models also include linear loss terms in the phytoplankton equation that represent either natural mortality or phytoplankton respiration (e.g.. Hood et ai, 2001). 

In summary, there appears to be evidence for both mechanisms of NH3/NH4 transport in bacterial cells. Passive difiFusion of NH3 would not generally lead to net accumulation by cells with an alkaline interior pH relative to the medium pH. Passive diffusion would be rate-limited by the low level of NH3 available at physiological pH and by the solubility properties of the cell membrane. NH4 active transport would be required for net ammonium uptake. However, net nitrogen accumulation could be accomplished by rapid assimilation of internal ammonia into amino acids. Net accumulation might be limited by the balance of the two processes uptake by active transport vs. loss by passive diffusion. 

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