نتایج جستجو برای: nitrogenase
تعداد نتایج: 2309 فیلتر نتایج به سال:
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...
The hydrolysis of ATP to ADP and P(i) is an integral part of all substrate reduction reactions catalyzed by nitrogenase. In this work, evidence is presented that nitrogenases isolated from Azotobacter vinelandii and Clostridium pasteurianum can hydrolyze MgGTP, MgITP, and MgUTP to their respective nucleoside diphosphates at rates comparable to those measured for MgATP hydrolysis. The reactions ...
Protonated states of the nitrogenase active site are mechanistically significant since substrate reduction is invariably accompanied by proton uptake. We report the low pH characterization by X-ray crystallography and EPR spectroscopy of the nitrogenase molybdenum iron (MoFe) proteins from two phylogenetically distinct nitrogenases (Azotobacter vinelandii, Av, and Clostridium pasteurianum, Cp) ...
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...
A distinctive characteristic of the Rhizobium genome is the frequent finding of reiterated sequences, which often constitute multigene families. Interestingly, these families usually maintain a high degree of nucleotide sequence identity. It is commonly assumed that apparent gene conversion between reiterated elements might lead to concerted variation among members of a multigene family. Howeve...
The mechanism for "NH4+ switch-off/on" of nitrogenase activity in Azospirillum brasilense and A. lipoferum was investigated. A correlation was established between the in vivo regulation of nitrogenase activity by NH4Cl or glutamine and the reversible covalent modification of dinitrogenase reductase. Dinitrogenase reductase ADP-ribosyltransferase (DRAT) activity was detected in extracts of A. br...
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...
Soybean (Glycine max L. Merr.) plants exposed to 10 mM KNO(3) for a 4 d period were used to test the correlation between nitrogenase activity, gene expression and sucrose metabolism. Nitrate caused the down-regulation of sucrose synthase (SS) transcripts within 1 d, although a decline in nodule SS activity and an increase in nodule sucrose content only occurred after 3-4 d. In a second experime...
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