Ammonium uptake by nitrogen fixing bacteria I. Azotobacter vinelandii.
Both the changes in the activities of nitrogenase, glutamine synthetase and glutamate dehydrogenase and in the extracellular and intracellular NH4+ concentrations were investigated during the transition from an NH4+ free medium to one containing NH4+ ions for a continuous culture of Azotobacter vinelandii. If added in amounts causing 80-100% repression of nitrogenase, ammonium acetate, lactate and phosphate are absorbed completely, whereas chloride, sulfate and citrate are only taken up to about 80%. After about 1-2 hrs the NH4+ remaining in the medium is absorbed too, indicating the induction or activation of a new NH4+ transport system. One of the new permeases allows the uptake of citrate in the presence of sucrose. Addition of inorganic NH4+ level leads to a reversible rise in the glutamine synthetase activity which is not prevented by chloramphenicol, and to a reversible decrease in nitrogenase activity. During these measurements glutamate dehydrogenase activity remains close to zero. The intracellular NH4+ level of about 0.6 mM does not change when extracellular NH4+ is taken up and repression of nitrogenase starts.
D000085:Acetates / Q000378:metabolism; D000643:Ammonium Chloride / Q000378:metabolism; D000645:Ammonium Sulfate / Q000378:metabolism; D000693:Anaerobiosis; D001395:Azotobacter / Q000201:enzymology / Q000378:metabolism*; D001692:Biological Transport; D002701:Chloramphenicol / Q000494:pharmacology; D002951:Citrates / Q000378:metabolism; D004794:Enzyme Repression; D005969:Glutamate Dehydrogenase / Q000378:metabolism; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism; D007773:Lactates / Q000378:metabolism; D009566:Nitrates / Q000378:metabolism; D009586:Nitrogen Fixation; D009591:Nitrogenase / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000378:metabolism*
D000085:Acetates; D002951:Citrates; D007773:Lactates; D009566:Nitrates; D000644:Quaternary Ammonium Compounds; D000643:Ammonium Chloride; D002701:Chloramphenicol; D009591:Nitrogenase; D005969:Glutamate Dehydrogenase; D005974:Glutamate-Ammonia Ligase; D000645:Ammonium Sulfate