Abstract
Pseudomonas aeruginosa, Ps. fluorescens and 3 marine psychrophylic pseudomonads were grown in chemostat cultures with nitrate ammonia or glutamate as nitrogen source. In cultures grown on nitrate (either carbon- or nitrogen-limited) and in ammonia nitrogen-limited cultures ammonia was assimilated via the GS/GOGAT pathway. With a excess of ammonia in the culture however ammonia was assimilated via GDH and GS was either present only at low levels or absent. Two distinct GDH activities were detected in all 5 bacteria, one specific to NAD and one to NADP. The presence of these activities was determined by the environment in which cells were grown. These activities showed differences with respect to substrate affinity (Km values) for ammonia, incubation temperature and to a lesser extent pH and may involve separate GDH isoenzymes. GS from the marine bacterium PL1 had a very high affinity for ammonia (Km of 0.3mm) but a low affinity for glutamate (Km of 19mm).
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Brown, C.M., Macdonald-Brown, D.S. & Stanley, S.O. The mechanisms of nitrogen assimilation in Pseudomonads. Antonie van Leeuwenhoek 39, 89–98 (1973). https://doi.org/10.1007/BF02578844
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DOI: https://doi.org/10.1007/BF02578844