ISSN:
1432-072X
Keywords:
Azotobacter vinelandii
;
Nitrogenase
;
Glutamine Synthetase
;
Ammonium Pool
;
Ammonium Transport
;
Citrate Transport
;
Repression
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract 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 + salts leads to acidification of the culture. Anaerobiosis suppresses NH4 + transport. A rise in the extracellular 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.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00447319
