نتایج جستجو برای: nitrogenase activity
تعداد نتایج: 1135737 فیلتر نتایج به سال:
During the enzymic reduction of N2 to NH3 by Mo-nitrogenase, free hydrazine (N2H4) is not detectable, but an enzyme-bound intermediate can be made to yield N2H4 by quenching the enzyme during turnover [Thorneley, Eady & Lowe (1978) Nature (London) 272, 557-558]. In contrast, we show here that the V-nitrogenase of Azotobacter chroococcum produces a small but significant amount of free N2H4 (up t...
Most naturally occurring strains of Rhizobium phaseoli possess reiteration of the nif genes. Three regions contain nitrogenase structural genes in strain CFN42. Two of these regions (a and b) have copies of nifH, nifD, and nifK, whereas the third region (c) contains only nifH. Strains containing mutations in either nif region a or nif region b had significantly diminished symbiotic effectivenes...
The nitrogen-deficient coastal waters of North Carolina contain suspended bacteria potentially able to fix N(2). Bioassays aimed at identifying environmental factors controlling the development and proliferation of N(2) fixation showed that dissolved organic carbon (as simple sugars and sugar alcohols) and particulate organic carbon (derived from Spartina alterniflora) additions elicited and en...
Discoveries in recent years have disclosed the importance of marine cyanobacteria in the context of primary production and global nitrogen cycling. It is hypothesized here that microbial mats in tropical coastal habitats harbour a rich diversity of previously uncharacterized cyanobacteria and that benthic marine nitrogen fixation in coastal zones is substantial. A polyphasic approach was used t...
Anabaena sp. CA fails to synthesize heterocysts and nitrogenase when grown with KNO3 as the nitrogen source. By contrast, both heterocysts and proheterocysts are synthesized in NH4Cl-containing media to a level nearly commensurate with cells grown in the absence of combined nitrogen. The growth rate of the organism in NH4Cl-containing media was similar to that obtained with KNO3 as the nitrogen...
Unlike most Pseudomonas, the root-associated bacterium Pseudomonas stutzeri A1501 fixes nitrogen after the horizontal acquisition of a nitrogen-fixing (nif) island. A genome-wide search for small noncoding RNAs (ncRNAs) in P. stutzeri A1501 identified the novel P. stutzeri-specific ncRNA NfiS in the core genome, whose synthesis was significantly induced under nitrogen fixation or sorbitol stres...
The effect of Mo on nitrate reductase and nitrogenase activities as well as the growth and mineral nutrition of wheat inoculated with Azospirillum brasilense in greenhouse pot experiments under drought stress conditions was evaluated. Plant dry weight and total N-yield appeared to be drastically affected by the severe drought stress. This inhibition was associated with a decline in nitrate redu...
Phytotron grown plants of Glycine max var. Caloria infected with Rhizobium japonicum 61-A-101 under controlled conditions as 14 d old seedlings develop a sharp maximum of nitrogenase activity of 13 i 3 nmol C2H4-h—'-mg nodule fresh weight1 19 d after infection, followed by a long period of reduced activity (3 —5 nmol) between 30 and 45 days after infection. A higher maximum activity (18 nmol C2...
No inhibition of nitrogenase activity by physiological levels of NH4+ or carbamyl phosphate was observed in extracts of Azotobacter vinelandii. All of the 15N2 reduced by cultures which received no NH4+ was found in the cells. By contrast, more than 95% of the 15N2 reduced by cultures which had been given NH4+ was found in the medium. Failure to examine the culture medium would lead to the erro...
HetR gene is a key regulator of heterocyst differentiation in filamentous cyanobacteria. It has been previously isolated and characterized from heterocystous cyanobacterium like Anabaena that has intercalary heterocysts and from non-heterocystous cyanobacteria like Trichodesmium and Symploca PCC 8002. This study reports the characterization of hetR gene from Cylindrospermum stagnale A1345, a cy...
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