The heterocyst-forming cyanobacterium Anabaena variabilis (ATCC 29413) is deficient in catalase activity, but especially heterocysts are rich in superoxide dismutase and peroxidases. It exhibits a light-dependent methylviologen-catalyzed oxygen uptake which is accompanied by a massive release o f hydrogen peroxide. Methylviologen caused a transient concentrationdependent inhibition o f nitrogen...

We describe a nitrogenase gene sequence database that facilitates analysis of the evolution and ecology of nitrogen-fixing organisms. The database contains 32 954 aligned nitrogenase nifH sequences linked to phylogenetic trees and associated sequence metadata. The database includes 185 linked multigene entries including full-length nifH, nifD, nifK and 16S ribosomal RNA (rRNA) gene sequences. E...

Experiments were conducted to determine the influence of Chlamydomonas sp. on nitrogen fixation (C(2)H(2) --> C(2)H(4)) in Azolla filiculoides and on the nitrogen fixation and growth of free-living Anabaena azollae 2B organisms. Inoculation of azolla medium with Chlamydomonas sp. was associated with decreased nitrogenase activity in A. filiculoides and with increases in the density of a fungal ...

To investigate the expression of specific symbiotic genes during the development of nitrogen-fixing root nodules, we conducted a systematic analysis of nodule-specific proteins and RNAs produced after the inoculation of alfalfa roots with a series of Rhizobium meliloti mutants generated by site-directed transposon Tn5 mutagenesis. The mutagenized region of the Rhizobium genome covered approxima...

Endophytic nitrogen fixing bacteria were isolated from the leaves, stems and roots of industrial variety (cv. U-Thong 3; UT3), wild and chewing sugarcane plants grown for 6 weeks in nitrogen (N)-free sand. Eighty nine isolates of endophytic bacteria were obtained on N-free agar. An acetylene reduction assay (ARA) detected nitrogenase activity in all 89 isolates. Three isolates from the chewing ...

Acetylene-reducing activity of detached pea nodules was determined by submerging the nodules in buffer solution [tris(hydroxymethyl)aminomethane-hydrochloride, pH 7.4] containing 100 mM sodium succinate and incubating under a gas phase of 90% O(2) and 10% C(2)H(2). The nitrogenase activity was 4 to 8 mumol of C(2)H(4) formed per g of nodule fresh weight per h and remained constant for at least ...

A novel, pulse-modulated spectroscopic system for measuring fractional leghemoglobin oxygenation and infected cell O(2) concentration (O(i)) in intact attached nodules of soybean (Glycine max) is described. The system is noninvasive and uses a pulsed (1000 Hertz) light-emitting diode coupled to an optical fiber to illuminate the nodule with light at 660 nanometer. A second optical fiber receive...

Nitrate-grown Azotobacter chroococcum ATCC 4412 cells lack the ability to fix N2. Nitrogenase activity developed after the cells were suspended in a combined nitrogen-free medium and was paralleled by a concomitant decrease in nitrate assimilation capacity. In such treated cells exhibiting transitory nitrate assimilation and N2-fixation capacity, nitrate or nitrite caused a short-term inhibitor...

We describe a nitrogenase gene sequence database that facilitates analysis of the evolution and ecology of nitrogen-fixing organisms. The database contains 32 954 aligned nitrogenase nifH sequences linked to phylogenetic trees and associated sequence metadata. The database includes 185 linked multigene entries including full-length nifH, nifD, nifK and 16S ribosomal RNA (rRNA) gene sequences. E...

Abstract Background Biological nitrogen fixation is catalyzed by Mo-, V- and Fe-nitrogenases that are encoded nif , vnf anf genes, respectively. NifB the key protein in synthesis of cofactors all nitrogenases. Most diazotrophic Paenibacillus strains have only one nifB gene located a compact cluster ( nifBHDKENX orf1 ) hesAnifV ). But some multiple genes their functions not known. Results A tota...