Selective inactivation of nitrogenase in Azotobacter vinelandii batch cultures.
AUTOR(ES)
Kleiner, D
RESUMO
When the exhaustion of sucrose or sulfate or the induction of encystment (by incubation in 0.2% beta-hydroxybutyrate) leads to termination of growth in Azotobacter vinelandii batch cultures, the nitrogenase levels in the organisms decreased rapidly, whereas glutamate synthase and glutamine synthetase levels remained unaltered. Glutamate dehydrogenase activities were low during the whole culture cycle, indicating that ammonia assimilation proceeds via glutamine. Toward depletion of sucrose or during induction of encystment, slight secretion of ammonia with subsequent reabsorption was occasionally observed, whereas massive ammonia excretion occurred when the sulfate became exhausted. The extracellular ammonia levels were paralleled by changes in the glutamine synthetase activity. The inactivation of the nitrogenase is explained as a result of rising oxygen tension, a consequence of a metabolic shift-down (reduced respiration) that occurs in organisms entering the stationary phase.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=232833Documentos Relacionados
- Protection of Nitrogenase in Azotobacter vinelandii
- Cellular ATP levels and nitrogenase switchoff upon oxygen stress in chemostat cultures of Azotobacter vinelandii.
- Inhibition of nitrogenase activity by ammonium chloride in Azotobacter vinelandii.
- Nature of Oxygen Inhibition of Nitrogenase from Azotobacter vinelandii
- Mutant of Azotobacter vinelandii That Hyperproduces Nitrogenase Component II