Cellular differentiation can be observed in certain filamentous blue-green algae after transfer of the cells from medium containing NH(4) (+) or NO(3) (-) to nitrogen-free medium. The appearance of differentiated cells (heterocysts) is accompanied by an increase in the activity of nitrogenase, an enzyme complex that reduces N(2) to NH(3). We have separated vegetative cells from heterocysts in d...

A large number of genes are necessary for the biosynthesis and activity of the enzyme nitrogenase to carry out the process of biological nitrogen fixation (BNF), which requires large amounts of ATP and reducing power. The multiplicity of the genes involved, the oxygen sensitivity of nitrogenase, plus the demand for energy and reducing power, are thought to be major obstacles to engineering BNF ...

Anabaena variabilis ATCC 29413 fixes nitrogen in specialized cells called heterocysts using either a Mo-nitrogenase or a V-nitrogenase. V-nitrogenase structural genes, vnfDGK, as well as vnfEN form an operon with ava4025, located upstream of vnfDG that is repressed by fixed nitrogen and by Mo. The ava4025-vnfDGKEN operon is under the control of a Mo-repressible promoter located nearly 600 bp up...

Soybean plants (Glycine max [L.] Merr) were grown in sand culture with 2 millimolar nitrate for 37 days and then supplied with 15 millimolar nitrate for 7 days. Control plants received 2 millimolar nitrate and 13 millimolar chloride and, after the 7-day treatment period, all plants were supplied with nil nitrate. The temporary treatment with high nitrate inhibited nitrogenase (acetylene reducti...

Ammonium suppresses nitrogenase activity in Anabaena flos-aquae (Lyng) Breb. at all pH values tested. l-Methionine-dl-sulfoximine at 1 millimolar totally inhibited glutamine synthetase, and 10 micromolar partially inhibited. Both concentrations protected nitrogenase activity from ammonium-induced suppression at pH 7.1 and 8.1. At pH 9.3 and 10.2, methionine sulfoximine did not alleviate the sup...

Nitrogen is the second most critical factor for crop production after water. In this study, the beneficial rhizobacterium Pseudomonas protegens Pf-5 was genetically modified to fix nitrogen using the genes encoding the nitrogenase of Pseudomonas stutzeri A1501 via the X940 cosmid. Pf-5 X940 was able to grow in L medium without nitrogen, displayed high nitrogenase activity and released significa...

SILVESTER, W. B., SILVESTER, J. K. , and TORREY, J. G. 1988. Adaptation of nitrogenase to varying oxygen tension and the role of the vesicle in root nodules of Alnus incana ssp. rugosa. Can. J . Bot. 66: 17721779. Growth of Alnus incana ssp. rugosa plants with root systems at Po2 levels of 5 , 21, and 40 kPa showed no significant differences among treatments over a 6-week period. Nitrogenase ac...

High-affinity vanadate transport systems have not heretofore been identified in any organism. Anabaena variabilis, which can fix nitrogen by using an alternative V-dependent nitrogenase, transported vanadate well. The concentration of vanadate giving half-maximum V-nitrogenase activity when added to V-starved cells was about 3 x 10(-9) M. The genes for an ABC-type vanadate transport system, vup...

When the MoFe (Kp1) and Fe (Kp2) component proteins of Klebsiella pneumoniae nitrogenase are incubated with MgADP and AlF4(-) in the presence of dithionite as a reducing agent, a stable putative transition-state complex is produced [Yousafzai and Eady (1997) Biochem. J. 326, 637-640]. Surprisingly, the EPR signal associated with reduced Kp2 is not detectable, but Kp1 retains the S=3/2 EPR signa...