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Dependence of oxygen-tolerant nitrogenase activity on divalent cations in Azotobacter vinelandii.

Department of Botany, Iowa State University, Ames 50011.

ABSTRACT

Nitrogenase activity of washed Azotobacter vinelandii cells was enhanced by the addition of Ca2+ and Mg2+, and the enhancement increased with the O2 concentration. In assays provided with a level of O2 that was initially supraoptimal and inhibitory to nitrogenase activity, the addition of Ca2+ or Mg2+ affected both the maximum respiration rate (Vmax) of the cells and the apparent affinity [KS(O2)] of cell respiration for O2. Changes in these parameters correlated with changes in nitrogenase activity. Aeration-dependent increases in Vmax and KS(O2) were inhibited by rifampin and chloramphenicol and were also observed in ammonium-grown cultures.

This article has been cited by other articles:

• Meek, L., Arp, D. J. (2000). The Hydrogenase Cytochrome b Heme Ligands of Azotobacter vinelandii Are Required for Full H2 Oxidation Capability. J. Bacteriol. 182: 3429-3436 [Abstract] [Full Text]