ISSN:
1432-072X
Keywords:
Ammonium metabolism
;
Ammonium transport
;
Glutamine synthetase
;
Nitrogenase
;
Glutamate synthase
;
Glutamate dehydrogenase
;
Nitrate reductase (dissimilatory)
;
Klebsiella pneumoniae
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract The primary steps of N2, ammonia and nitrate metabolism in Klebsiella pneumoniae grown in a continuous culture are regulated by the kind and supply of the nitrogenous compound. Cultures growing on N2 as the only nitrogen source have high activities of nitrogenase, unadenylated glutamine synthetase and glutamate synthase and low levels of glutamate dehydrogenase. If small amounts of ammonium salts are added continuously, initially only part of it is absorbed by the organisms. After 2–3 h complete absorption of ammonia against an ammonium gradient coinciding with an increased growth rate of the bacteria is observed. The change in the extracellular ammonium level is paralleled by the intracellular glutamine concentration which in turn regulates the glutamine synthetase activity. An increase in the degree of adenylation correlates with a repression of nitrogenase synthesis and an induction of glutamate dehydrogenase synthesis. Upon deadenylation these events are reversed.—After addition of nitrate ammonia appears in the medium, probably due to the action of a membrane bound dissimilatory nitrate reductase.—Addition of dinitrophenol causes transient leakage of intracellular ammonium into the medium.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00446553
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