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  • Ammonium metabolism  (1)
  • Ammonium uptake  (1)
  • Azotobacter vinelandii  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Ammonium (methylammonium) uptake by Alcaligenes eutrophus H16 (1986)
    Springer
    Archives of microbiology 145 (1986), S. 306-310 
    Details
    ISSN: 1432-072X
    Keywords: Ammonium uptake ; Methylammonium ; Nitrogen control ; Cold shock ; Alcaligenes eutrophus H16
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The uptake of the radioactive ammoniumanalogue 14C-methylammonium1 was measured in heterotrophically grown cells of Alcaligenes eutrophus H16 in order to study the mechanism of NH 4 + uptake. MA gradients of up to 200 were built up by a substrate-specific and energy-dependent system which showed a K m of 35–111 μM and a V max of 0.4–1.8 nmol MA/min per mg protein. The involved carrier exhibited a higher affinity towards NH 4 + than towards CH3NH 3 + indicating that ammonium rather than MA was its natural substrate. Cold shock with hypotonic but not with hypertonic solutions caused the efflux of almost the entire accumulated MA. Osmotic shock did not affect the uptake reaction, suggesting that no periplasmic binding proteins were involved. Indirect observations indicate the membrane potential as driving force for MA uptake. High rates of uptake were observed in cells grown under nitrogen deficiency or with nitrate as nitrogen source. The uptake rate decreased during growth at high ammonium concentrations indicating that biosynthesis of nitrogenous compounds was supported by passive diffusion of NH3. The data suggest that the formation of the carrier is subject to “nitrogen control”.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00470862
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  • 2
    Electronic Resource
    Electronic Resource
    Degradation of the nitrogenase proteins during encystment of Azotobacter vinelandii (1986)
    Springer
    Archives of microbiology 145 (1986), S. 287-289 
    Details
    ISSN: 1432-072X
    Keywords: Azotobacter vinelandii ; Encystment ; Nitrogenase ; Protein degradation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrogenase activity in cell-free extracts of Azotobacter vinelandii declines during encystment. Upon germination a rapid increase in activity is observed, which is suppressed by rifampicin, suggesting that de novo biosynthesis of the nitrogenase proteins is required. The decline of activity during encystment is accompanied by disappearance of both nitrogenase proteins from cell extracts, indicating irreversible proteolysis. Total proteinase activity does not change significantly during encystment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00443660
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  • 3
    Electronic Resource
    Electronic Resource
    Ammonia-excreting mutants ofKlebsiella pneumoniae with a pleiotropic defect in nitrogen metabolism (1996)
    Springer
    Archives of microbiology 166 (1996), S. 388-393 
    Details
    ISSN: 1432-072X
    Keywords: Ammonium metabolism ; glnAntrBC ; Nitrogenase regulation ; Nitrogen control ; Ammonia excretion ; Amino acid utilization ; Ntr
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Enterobacterial mutants defective in the nitrogen control regulatory system (Ntr) generally display a pleiotropic phenotype with regard to expression and regulation of several enzymes and transport systems involved in the assimilation of N sources. This report describes the isolation and characterization of similar pleiotropic mutants ofKlebsiella pneumoniae that cannot be complemented byntr genes. The strains excreted ammonia, were unable to grow on a number of N sources, and contained low glutamine:2-oxoglutarate amino transferase and normal, but unmodifiable glutamine synthetase activities and a nitrogenase level largely unaffected by ammonium, but still repressible by an amino acid mixture. Genetic studies suggested that this phenotype is due to overexpression of an unknown regulatory protein.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01682984
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