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Nitrogen fixation

About: Nitrogen fixation is a research topic. Over the lifetime, 7940 publications have been published within this topic receiving 232921 citations. The topic is also known as: GO:0009399.


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Journal ArticleDOI
TL;DR: In this article, the expression of many nitrogen assimilation genes is subjected to regulation being activated by the nitrogen control transcription factor NtcA, which is autoregulatory and whose activity appears to be influenced by 2-oxoglutarate and the signal transduction protein PII.
Abstract: Nitrogen sources commonly used by cyanobacteria include ammonium, nitrate, nitrite, urea and atmospheric N2, and some cyanobacteria can also assimilate arginine or glutamine. ABC (ATP-binding cassette)-type permeases are involved in the uptake of nitrate/nitrite, urea and most amino acids, whereas secondary transporters take up ammonium and, in some strains, nitrate/nitrite. In cyanobacteria, nitrate and nitrite reductases are ferredoxin-dependent enzymes, arginine is catabolized by a combination of the urea cycle and arginase pathway, and urea is degraded by a Ni2+-dependent urease. These pathways provide ammonium that is incorporated into carbon skeletons through the glutamine synthetase–glutamate synthase cycle, in which 2-oxoglutarate is the final nitrogen acceptor. The expression of many nitrogen assimilation genes is subjected to regulation being activated by the nitrogen-control transcription factor NtcA, which is autoregulatory and whose activity appears to be influenced by 2-oxoglutarate and the signal transduction protein PII. In some filamentous cyanobacteria, N2 fixation takes place in specialized cells called heterocysts that differentiate from vegetative cells in a process strictly controlled by NtcA. Abbreviations: ABC, ATP-binding cassette; CAP, catabolite gene activator protein

260 citations

Journal ArticleDOI
TL;DR: More than 200 angiosperms, distributed in 25 genera, develop root nodule symbioses (actinorhizas) with soil bacteria of the actinomycetous genus Frankia as mentioned in this paper.
Abstract: summary More than 200 angiosperms, distributed in 25 genera, develop root nodule symbioses (actinorhizas) with soil bacteria of the actinomycetous genus Frankia. Although most soils studied contain infective Frankia, cultured strains are available only after isolation from root nodules. Frankia infects roots via root hairs in some hosts or via intercellular penetration in others. The nodule originates in the pericycle. The number of nodules in Alnus is determined by the plant in an autoregulated process that, in turn, is modulated by nutrients such as nitrogen and phosphate. Except in the genera Allocausarina and Casuarina, Frankia in nodules develops so-called vesicles where nitrogenase is localized. Sporulation of Frankia occurs in some symbioses. As a group, actinorhizal plants show a large range of anatomical and biochemical adaptations in order to balance the oxygen tension near nitrogenase. In symbioses with well aerated nodule tissue like Alnus, the vesicles have a multilayered envelope composed mainly of lipids, bacterio-hopanetetrol and their derivatives. This envelope is assumed to retard the diffusion of oxygen into the nitrogenase-containing vesicle. In symbioses like Casuarina, the infected plant cells themselves, rather than Frankia, appear to retard oxygen diffusion, and high concentrations of haemoglobin indicate an infected region with a low oxygen tension. At least in Alnus spp., ammonia resulting from N2 fixation is assimilated by glutamine synthetase in the plant. The carbon compound(s) used by Frankia in nodules is not yet known. Nitrogenase activity decreases in response to a number of environmental factors but recovers upon return to normal conditions. This dynamism in nitrogenase activity is often explained by loss and recovery of active nitrogenase and has been traced to loss and recovery of the nitrogenase proteins themselves. Recovery is partly due to growth of Frankia and to development of new vesicles in the Alnus nodules. In the field, varying conditions continuously affect the plants and the measured rate of N2 fixation is a result not only of the conditions prevailing at the moment but also of the conditions experienced over preceding days. N2 fixed by actinorhizal plants is substantial and actinorhizal plants have great potential in soil reclamation and in various types of forestry. Several species are also useful in horticulture.

259 citations

Journal ArticleDOI
14 Sep 2007-Science
TL;DR: With multi-isotope imaging mass spectrometry, this approach directly imaged and measured nitrogen fixation by individual bacteria within eukaryotic host cells and demonstrated that fixed nitrogen is used for host metabolism.
Abstract: Biological nitrogen fixation, the conversion of atmospheric nitrogen to ammonia for biosynthesis, is exclusively performed by a few bacteria and archaea. Despite the essential importance of biological nitrogen fixation, it has been impossible to quantify the incorporation of nitrogen by individual bacteria or to map the fate of fixed nitrogen in host cells. In this study, with multi-isotope imaging mass spectrometry we directly imaged and measured nitrogen fixation by individual bacteria within eukaryotic host cells and demonstrated that fixed nitrogen is used for host metabolism. This approach introduces a powerful way to study microbes and global nutrient cycles.

258 citations

Journal ArticleDOI
TL;DR: Rates of release of DON showed considerable variation within replicate experiments and were variable depending on time of day and duration of time course experiments, likely a significant source of new nitrogen for the associated bacteria or the non-nitrogen-fixing filaments of the Trichodesmium colonies.
Abstract: Trichodesmium sp. is a filamentous, colonial cyanobacterium which contributes substantially to the input of nitrogen in tropical and subtropical oceanic waters through nitrogen fixation (N2 fixation). We applied a 15N tracer technique to assess the rate of release of dissolved organic nitrogen (DON) from this cyanobacterium and compared those rates with rates of N2 fixation determined for the same assemblages at the same times of day. Rates of release of DON showed considerable variation within replicate experiments and were variable depending on time of day and duration of time course experiments. On average, rates of DON release were ca. 50% the rates of N2 fixation. We also fractionated the DON released by using ultrafiltration and found that 60 to 80% of the total organic release was of the size class <10,000 Da. The release of these organic compounds by Trichodesmium spp. is likely a significant source of new nitrogen for the associated bacteria or the non-nitrogen-fixing filaments of the Trichodesmium colonies.

257 citations

Book ChapterDOI
TL;DR: A recent15N dilution/N balance study confirmed that certain sugar cane varieties are capable of obtaining large contributions of nitrogen from plant-associated N2 fixation, and under good conditions of water and mineral nutrient supply, it may be possible to dispense with N fertilization of these varieties altogether.
Abstract: A recent 15N dilution/N balance study confirmed that certain sugar cane varieties are capable of obtaining large contributions of nitrogen from plant-associated N2 fixation. It was estimated that up to 60 to 80% of plant N could be derived from this source, and under good conditions of water and mineral nutrient supply, it may be possible to dispense with N fertilization of these varieties altogether. The recently discovered bacterium, Acetobacter diazotrophicus, apparently responsible for this N2 fixation associated with the plants, has unique physiological properties for a diazotroph, such as tolerance to low pH, and high sugar and salt concentrations, lack of nitrate reductase, and nitrogenase activity which tolerates short-term exposure to ammonium. Furthermore, it also behaves as an endophyte, in that it is unable to infect sugar cane plants unless through damaged tissue or by means of VA mycorrhizae and is propagated via the planting material (stem pieces).

252 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023390
2022831
2021263
2020240
2019250
2018261