Biological nitrogen fixation is an important source of fixed nitrogen for the biosphere. Microorganisms catalyse biological nitrogen fixation with the enzyme nitrogenase, which has been highly conserved through evolution. Cloning and sequencing of one of the nitrogenase structural genes, nifH, has provided a large, rapidly expanding database of sequences from diverse terrestrial and aquatic env...

Peribacteroid membrane vesicles from pea (Pisum sativum) root nodules were isolated from membrane-enclosed bacteroids by an osmotic shock. The ATPase activity associated with this membrane preparation was characterized, and its electrogenic properties were determined. The pH gradient was measured as a change of the fluorescence intensity of 9-amino-6-chloro-2-methoxyacridine and the membrane po...

A method was devised that allows measurement in vivo of hydrogenase-catalysed H2 evolution from the cyanobacterium Anabaena cylindrica, independent of nitrogenase activity, which is also present. Addition of low concentrations of reduced Methyl Viologen (1-10mM) to intact heterocystous filaments of the organism resulted in H2 evolution, but produced conditions giving total inhibition of nitroge...

The ability to utilize atmospheric nitrogen (N(2)) as a sole nitrogen source is an important trait for prokaryotes. Knowledge of N(2) fixation by methanotrophs is needed to understand their role in nitrogen cycling in different environments. The verrucomicrobial methanotroph 'Methylacidiphilum fumariolicum' strain SolV was investigated for its ability to fix N(2). Physiological studies were com...

SILVESTER, W. B., WHITBECK, J . , SILVESTER, J. K., and TORREY, J. G. 1988. Growth, nodule morphology, and nitrogenase activity of Myrica gale with roots grown at various oxygen levels. Can. J . Bot. 66: 17621771. Myrica gale L. plants were inoculated with Frankia strain HFP M'gI5 and grown for 28 days with root systems exposed to 2, 5, 10, 21, and 40 kPa 0,. Plant growth was similar under all ...

Bacterial Nitrogenase, Nitrite Inhibition, Dinitrogenase Reductase Dinitrogen fixation by crude extracts from Rhodopseudomonas palustris and Rhodomicrobium vannielii and by purified nitrogenase preparations from Azotobacter vinelandii and Clostridium pasteurianum is inhibited by nitrite, whereas in the same preparations nitrate is without effect. In Clostridium nitrite seems to interact with di...

abstract osmoreguolation is a physiological processes that plant cell uses to maintain water balance and it is generally caused by metabolite accumulation inside the cell. inoculated legumes by some drought tolerant sinorhizobium isolates helps osmoreguolation by increasing biological nitrogen fixation. in order to find some drought tolerant sinorhizobium isolates, 80 isolates were isolated and...

Klebsiella pneumoniae accumulates molybdenum during nitrogenase derepression. The molybdenum is primarily in nitrogenase component I in the form of iron-molybdenum cofactor (FeMo-co). Mutations in any of three genes (nifB, nifN, and nifE) involved in the biosynthesis of FeMo-co resulted in very low molybdenum accumulation and in a molybdenum-free nitrogenase component I. A mutant lacking both s...

The filamentous cyanobacterium Anabaena variabilis fixes nitrogen in the presence of vanadium (V) and in the absence of molybdenum (Mo), using a V-dependent nitrogenase (V-nitrogenase) encoded by the vnfDGK genes. Downstream from these genes are two genes that are similar to the vnfEN genes of Azotobacter vinelandii. Like the vnfDGK genes, the vnfEN genes were transcribed in the absence of Mo, ...

The activity of nitrogen fixation measured by acetylene reduction was examined in chemosynthetic microbial mats at 72-75°C in slightly-alkaline sulfidic hot springs in Nakabusa, Japan. Nitrogenase activity markedly varied from sampling to sampling. Nitrogenase activity did not correlate with methane production, but was detected in samples showing methane production levels less than the maximum ...