Ammonium uptake by nitrogen fixing bacteria I. Azotobacter vinelandii

Arch Microbiol. 1975 Jun 22;104(2):163-9. doi: 10.1007/BF00447319.


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.

MeSH terms

  • Acetates / metabolism
  • Ammonium Chloride / metabolism
  • Ammonium Sulfate / metabolism
  • Anaerobiosis
  • Azotobacter / enzymology
  • Azotobacter / metabolism*
  • Biological Transport
  • Chloramphenicol / pharmacology
  • Citrates / metabolism
  • Enzyme Repression
  • Glutamate Dehydrogenase / metabolism
  • Glutamate-Ammonia Ligase / metabolism
  • Lactates / metabolism
  • Nitrates / metabolism
  • Nitrogen Fixation*
  • Nitrogenase / metabolism
  • Quaternary Ammonium Compounds / metabolism*


  • Acetates
  • Citrates
  • Lactates
  • Nitrates
  • Quaternary Ammonium Compounds
  • Ammonium Chloride
  • Chloramphenicol
  • Nitrogenase
  • Glutamate Dehydrogenase
  • Glutamate-Ammonia Ligase
  • Ammonium Sulfate