Artículos de revistas: "Ammonium assimilation"

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Palaniappan, C. y M. Gunasekaran. "Ammonium assimilation inNocardia asteroides". Mycopathologia 124, n.º 2 (noviembre de 1993): 69–72. http://dx.doi.org/10.1007/bf01103104.

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Muro-Pastor, M. Isabel, Jose C. Reyes y Francisco J. Florencio. "Ammonium assimilation in cyanobacteria". Photosynthesis Research 83, n.º 2 (febrero de 2005): 135–50. http://dx.doi.org/10.1007/s11120-004-2082-7.

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3

Kerby, Nigel W., Peter Rowell y William D. P. Stewart. "Cyanobacterial ammonium transport, ammonium assimilation, and nitrogenase regulation". New Zealand Journal of Marine and Freshwater Research 21, n.º 3 (septiembre de 1987): 447–55. http://dx.doi.org/10.1080/00288330.1987.9516240.

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4

Tesch, M., A. A. de Graaf y H. Sahm. "In Vivo Fluxes in the Ammonium-Assimilatory Pathways in Corynebacterium glutamicum Studied by15N Nuclear Magnetic Resonance". Applied and Environmental Microbiology 65, n.º 3 (1 de marzo de 1999): 1099–109. http://dx.doi.org/10.1128/aem.65.3.1099-1109.1999.

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ABSTRACT Glutamate dehydrogenase (GDH) and glutamine synthetase (GS)–glutamine 2-oxoglutarate-aminotransferase (GOGAT) represent the two main pathways of ammonium assimilation in Corynebacterium glutamicum. In this study, the ammonium assimilating fluxes in vivo in the wild-type ATCC 13032 strain and its GDH mutant were quantitated in continuous cultures. To do this, the incorporation of15N label from [15N]ammonium in glutamate and glutamine was monitored with a time resolution of about 10 min with in vivo 15N nuclear magnetic resonance (NMR) used in combination with a recently developed high-cell-density membrane-cyclone NMR bioreactor system. The data were used to tune a standard differential equation model of ammonium assimilation that comprised ammonia transmembrane diffusion, GDH, GS, GOGAT, and glutamine amidotransferases, as well as the anabolic incorporation of glutamate and glutamine into biomass. The results provided a detailed picture of the fluxes involved in ammonium assimilation in the two different C. glutamicumstrains in vivo. In both strains, transmembrane equilibration of 100 mM [15N]ammonium took less than 2 min. In the wild type, an unexpectedly high fraction of 28% of the NH4 + was assimilated via the GS reaction in glutamine, while 72% were assimilated by the reversible GDH reaction via glutamate. GOGAT was inactive. The analysis identified glutamine as an important nitrogen donor in amidotransferase reactions. The experimentally determined amount of 28% of nitrogen assimilated via glutamine is close to a theoretical 21% calculated from the high peptidoglycan content of C. glutamicum. In the GDH mutant, glutamate was exclusively synthesized over the GS/GOGAT pathway. Its level was threefold reduced compared to the wild type.

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Ruamrungsri, Sakchai, Soraya Ruamrungsri, Taro Ikarashi y Takuji Ohyama. "Ammonium and nitrate assimilation inNarcissusroots". Journal of Horticultural Science and Biotechnology 75, n.º 2 (enero de 2000): 223–27. http://dx.doi.org/10.1080/14620316.2000.11511227.

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6

Hew, C. S., L. Y. Lim y C. M. Low. "Nitrogen assimilation in orchids". HortScience 27, n.º 6 (junio de 1992): 680f—680. http://dx.doi.org/10.21273/hortsci.27.6.680f.

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The uptake of nitrate and ammonium by a terrestial (Bromheadia finlaysonia) and an epiphytic (Dendrobium hybrid) orchid in solution culture has been studied. The rates of nitrate and ammonium were relatively linear, with higher rate of uptake for ammonium. The rates of nitrate uptake in terrestial and epiphytic orchids were 0.4 and 0.9 μmole gm fw-1 hr-1 respectively and they were considerably lower than those of most major crops. SEM studies show that the velamen of Bromheadia was 2 cells thick whereas that of Dendrobium was 8-10 cells thick. It is unlikely that the velamen is the major factor in restricting influx of nitrate or ammonium. Nitrate reductase (NR) and glutamine synthetase (GS) were present in roots and leaves of both orchids. NR was high in roots but low in leaves. The reverse was for GS. The activities of NR and GS was low but high enough to account for the rate of nitrate or ammonium uptake. It appears that the movement of ions across the transfer junction at the exodermis plays a major regulatory role in ion uptake by orchid root.

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7

Boyce, Richard L., Andrew J. Friedland, C. Page Chamberlain y Simon R. Poulson. "Direct canopy nitrogen uptake from 15N-labeled wet deposition by mature red spruce". Canadian Journal of Forest Research 26, n.º 9 (1 de septiembre de 1996): 1539–47. http://dx.doi.org/10.1139/x26-173.

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We applied 15N-labeled ammonium and nitrate to individual branches of red spruce (Picearubens Sarg.) to examine the importance of canopy N assimilation in the field. Levels of labeled N were highest in the youngest foliage and youngest twigs, and twig ammonium assimilation exceeded nitrate assimilation. Approximately 5% of the ammonium and 1% of the nitrate applied to each branch was assimilated; because of throughfall interactions with multiple branches, canopy assimilation rates are expected to be 3–6 times larger. Twig 15N levels exceeded foliar levels for the younger age-classes in the ammonium-labeled treatments, suggesting that twigs play an important role in ammonium assimilation. Comparisons of these results with data from trees that assimilated 15N through their roots showed that the pattern of canopy N assimilation differs from root assimilation, primarily by the assimilation of large amounts of N by twigs. Our results directly demonstrate for the first time that canopy assimilation is a pathway for uptake of N in these high-elevation trees. Canopy assimilation of atmospherically deposited N may represent 2–8% of the total N requirement for spruce in the high-elevation forest. While canopy N assimilation may thus reflect only a minor anthropogenic alteration of N acquisition in these forests, the long-term fate of this N needs to be determined.

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8

Muro-Pastor, M. Isabel y Francisco J. Florencio. "Regulation of ammonium assimilation in cyanobacteria". Plant Physiology and Biochemistry 41, n.º 6-7 (junio de 2003): 595–603. http://dx.doi.org/10.1016/s0981-9428(03)00066-4.

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9

Amine, J., R. Marczak, N. Maazouzi y E. Masion. "Regulation of ammonium assimilation byClostridium acetobutylicum". Journal of Basic Microbiology 30, n.º 9 (1990): 635–42. http://dx.doi.org/10.1002/jobm.3620300904.

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10

Novák, J., E. Čurdová, V. Jechová, E. Cimburková y Z. Vaněk. "Enzymes of ammonium assimilation inStreptomyces avermitilis". Folia Microbiologica 37, n.º 4 (agosto de 1992): 261–66. http://dx.doi.org/10.1007/bf02814560.

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11

Holmes, Ann R., Graeme S. McNaughton, Ray D. More y Maxwell G. Shepherd. "Ammonium assimilation by Candida albicans and other yeasts: a 13N isotope study". Canadian Journal of Microbiology 37, n.º 3 (1 de marzo de 1991): 226–32. http://dx.doi.org/10.1139/m91-034.

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Nuclear magnetic resonance spectra of cultures of Candida albicans incubated in the presence of 15N-labelled ammonium demonstrated that glutamine and glutamate were the only initial products of ammonium assimilation. The nature of the route of assimilation in the yeasts Candida albicans, Saccharomyces cerevisiae, and Candida tropicalis was further examined by the use of the short-lived isotope 13N. [13N]ammonium was generated in the reaction 16O(p,α)13N, induced by proton bombardment of water in a tandem accelerator. High-pressure liquid chromatography was used to separate and identify the products of assimilation, and radioactivity was detected and corrected for decay, using a computer-linked Nal scintillation detector. In the three yeasts studied, the labelled ammonium was assimilated into the acid-extractable fraction of cell suspensions within 1 min, and over 75% was converted to glutamine and glutamate. Subsequent to exhaustion of the labelled ammonium, the stoichiometry of the distribution of radiolabel was consistent with a net transfer of radiolabel from glutamine to glutamate, confirming the operation of glutamate synthase (EC 1.4.1.14) in these yeasts. Initial assimilation of label was mostly into glutamine (at a maximal rate within 10 s in C. albicans), whereas accumulation in glutamate did not occur at maximal rate until more than 70% of the labelled ammonium had been assimilated (between 30 and 60 s in C. albicans). We conclude that the glutamine synthetase – glutamate synthase pathway is the major route of ammonium assimilation in C. albicans and also in nitrogen-starved cultures of S. cerevisiae and C. tropicalis. Key words: Candida albicans, ammonium assimilation, nitrogen.

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12

Rochester, IJ, GA Constable y DA Macleod. "Preferential nitrate immobilization in alkaline soils". Soil Research 30, n.º 5 (1992): 737. http://dx.doi.org/10.1071/sr9920737.

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The literature pertaining to N immobilization indicates that ammonium is immobilized in preference to nitrate. Our previous research in an alkaline clay soil has indicated substantial immobilization of nitrate. To verify the preference for immobilization of nitrate or ammonium by the microbial biomass in this and other soil types, the immobilization of ammonium and nitrate from applications of ammonium sulfate and potassium nitrate following the addition of cotton crop stubble was monitored in six soils. The preference for ammonium or nitrate immobilization was highly correlated with each soil's pH, C/N ratio and its nitrification capacity. Nitrate was immobilized in preference to ammonium in neutral and alkaline soils; ammonium was preferentially immobilized in acid soils. No assimilation of nitrate (or nitrification) occurred in the most acid soil. Similarly, little assimilation of ammonium occurred in the most alkaline soil. Two physiological pathways, the nitrate assimilation pathway and the ammonium assimilation pathway, appear to operate concurrently; the dominance of one pathway over the other is indicated by soil pH. The addition of a nitrification inhibitor to an alkaline soil enhanced the immobilization of ammonium. Recovery of 15N confirmed that N was not denitrified, but was biologically immobilized. The immobilization of 1 5 ~ and the apparent immobilization of N were similar in magnitude. The identification of preferential nitrate immobilization has profound biological significance for the cycling of N in alkaline soils.

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13

Wild, Aloysius y Christine Ziegler. "The Effect of Bialaphos on Ammonium-Assimilation and Photosynthesis I. Effect on the Enzymes of Ammonium-Assimilation". Zeitschrift für Naturforschung C 44, n.º 1-2 (1 de febrero de 1989): 97–102. http://dx.doi.org/10.1515/znc-1989-1-217.

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Abstract In this investigation, the effect of bialaphos (phosphinothricyl-alanyl-alanine) on the enzymes involved in NH4+-assimilation - glutamine synthetase, glutamine-2-oxoglutarate aminotransferase, glutamate dehydrogenase - is examined and compared to the effect of phosphinothricin (glufosinate) on the same enzymes. Bialaphos was given to whole plants (in vivo) and to leaf homogenate (in vitro). The investigation showed that bialaphos has an inhibiting effect on glutamine synthetase in vivo, but not in vitro. In contrast to this, phosphinothricin inhibits glutamine synthetase in vitro as well as in vivo. It was found that bialaphos, similar to phosphinothricin, does not inhibit glutamine-2-oxoglutarate aminotransferase and glutamate dehydrogenase in vivo or in vitro. Only at bialaphos concentrations exceeding 10 mM, there is an inhibition of glutamate dehydrogenase in vitro. Using radioactive [3H]bialaphos (phosphinothricyl-3H-alanyl-alanine) it could be demonstrated that in the plant, bialaphos is split into phosphinothricin and alanine. The phosphinothricin released is probably the active herbicide component. Consequently, the herbicidal effects of phosphinothricin and bialaphos are the same.

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14

Wang, J. y AE Douglas. "Nitrogen recycling or nitrogen conservation in an alga-invertebrate symbiosis?" Journal of Experimental Biology 201, n.º 16 (15 de agosto de 1998): 2445–53. http://dx.doi.org/10.1242/jeb.201.16.2445.

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When corals and allied animals are deprived of their symbiotic algae, the ammonium content in their tissues rises. This is commonly interpreted as evidence for nitrogen recycling (i.e. algal assimilation of animal waste ammonium into amino acids that are released back to the animal), but it can also be explained as nitrogen conservation by the animal (i.e. reduced net ammonium production in response to the receipt of algal photosynthetic carbon). This study discriminated between these interpretations in two ways. First, the increased ammonium concentration in the sea anemone Aiptasia pulchella, caused by darkness or depletion of the alga Symbiodinium, was partially or completely reversed by supplementing the medium with organic carbon compounds (e.g. <IMG src="/images/symbols/&agr ;.gif" WIDTH="9" HEIGHT="12" ALIGN= "BOTTOM" NATURALSIZEFLAG="3">-ketoglutarate). Second, the activity of the ammonium-assimilating enzyme glutamine synthetase and the concentration of protein amino acids in the free amino acid pool of the animal, which were depressed by darkness and algal depletion, were restored by exogenous carbon compounds. It is concluded that organic carbon, whether derived from algal photosynthate or exogenously, promotes the animal's capacity for ammonium assimilation and reduces ammonium production from amino acid degradation. These processes contribute to nitrogen conservation in the animal, but they confound the interpretation of various studies on nitrogen recycling by symbiotic algae.

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15

Monselise, Edna Ben-Izhak y Daniel Kost. "15N NMR SPECTROSCOPIC STUDY OF AMMONIUM ION ASSIMILATION BY SPIRODELA OLIGORRHIZA—LEMNACEAE—AS AFFECTED BY LIGHT AND CARBON SUPPLY IN GREEN AND EXTOLIATED PLANTS". Israel Journal of Plant Sciences 46, n.º 4 (13 de mayo de 1998): 255–64. http://dx.doi.org/10.1080/07929978.1998.10676734.

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Nitrogen assimilation and amino acid production in Spirodela oligorrhiza plants exposed to 30 mM 15NH4Cl was studied using l5N NMR spectroscopy. Green and etiolated plants were studied under different light regimes and in the presence of added carbon, either as sucrose or as α-ketoglutarate. Etiolated plants are capable of ammonium assimilation and, as in green plants, this occurs via the glutamine synthetase/glutamine oxoglutarate amine transferase (GS/GOGAT) and the aspartate aminotransferase/asparagine synthetase pathways. The major assimilation products in both etiolated and green plants were glutamine and asparagine. Thus our results confirm that N-amides are key detoxification products when plants are exposed to external ammonium ion, and act as storage reservoirs or sinks for assimilated ammonium. In plants grown under continuous light, ammonium ion was taken up and assimilated to completion. L-methionine DL-sulfoximine, a GS inhibitor, inhibited ammonium ion assimilation but not its uptake. Addition of azaserine, a GOGAT inhibitor, resulted in the disappearance of α-amino signals, and l5N incorporation into the glutamine amide-N position only. This is evidence for the operation of the GS/GOGAT pathway, as opposed to the glutamate dehydrogenase (GDH) pathway, in both green and etiolated plants. Even in the dark and under various stress conditions, no sign of ammonium ion assimilation via the GDH pathway could be detected. The amount of amino acid metabolites strongly depended on the light regime and the extent of external carbon supply. Supply of α-ketoglutarate to the etiolated plants increased ammonium ion uptake and assimilation. Ornithine and arginine were also formed, consistent with the operation of the ornithine cycle.

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Bessagnet, Bertrand, Laurent Menut, Florian Couvidat, Frédérik Meleux, Guillaume Siour y Sylvain Mailler. "What Can We Expect from Data Assimilation for Air Quality Forecast? Part II: Analysis with a Semi-Real Case". Journal of Atmospheric and Oceanic Technology 36, n.º 7 (julio de 2019): 1433–48. http://dx.doi.org/10.1175/jtech-d-18-0117.1.

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AbstractAssimilation of observational data from ground stations and satellites has been identified as a technique to improve air quality model results. This study is an evaluation of the maximum benefit expected from data assimilation in chemical transport models. Various tests are performed under real meteorological conditions; the injection of various subsets of “simulated observational data” at the initial state of a forecasting period is analyzed in terms of benefit on selected criteria. This observation dataset is generated by a simulation with perturbed input data. Several criteria are defined to analyze the simulations leading to the definition of a “tipping time” to compare the behavior of simulations. Assimilating three-dimensional data instead of ground observations clearly adds value to the forecast. For the studied period and considering the expected best favorable data assimilation experiment, the maximum benefit is higher for particulate matter (PM) with tipping times exceeding 80 h; for ozone (O3) the gain is on average around 30 h. Assimilating O3 concentrations with a delta calculated on the first level and propagated over the vertical direction provides better results on O3 mean concentrations when compared with the expected best experiment corresponding to the injection of the O3 “observations” 3D dataset, but for maximum O3 concentrations the opposite behavior is observed. If data assimilation of secondary pollutant concentrations provides an improvement, assimilation of primary pollutant emissions can have beneficial impacts when compared with an assimilation of concentrations, after several days on secondary pollutants like O3 or nitrate concentrations and more quickly for the emitted primary pollutants. An assimilation of ammonia concentrations has slightly better performances on nitrate, ammonium, and PM concentrations relative to the assimilation of nitrogen or sulfur dioxides.

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17

Guy, Robert D., Greg C. Vanlerberghe y David H. Turpin. "Significance of Phosphoenolpyruvate Carboxylase during Ammonium Assimilation". Plant Physiology 89, n.º 4 (1 de abril de 1989): 1150–57. http://dx.doi.org/10.1104/pp.89.4.1150.

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18

CHALOT, M., G. R. STEWART, A. BRUN, F. MARTIN y B. BOTTON. "Ammonium assimilation by spruce-Hebeloma sp. ectomycorrhizas". New Phytologist 119, n.º 4 (diciembre de 1991): 541–50. http://dx.doi.org/10.1111/j.1469-8137.1991.tb01046.x.

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19

Cacciari, Isabella, Daniela Lippi, Tito Pietrosanti y Walter Pietrosanti. "Ammonium assimilation in an Arthrobacter sp. ?fluorescens?" Archives of Microbiology 145, n.º 2 (julio de 1986): 113–15. http://dx.doi.org/10.1007/bf00446766.

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20

Flynn, Kevin J., Michael J. R. Fasham y Charles R. Hipkin. "Modelling the interactions between ammonium and nitrate uptake in marine phytoplankton". Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences 352, n.º 1361 (29 de noviembre de 1997): 1625–45. http://dx.doi.org/10.1098/rstb.1997.0145.

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An empirically based mathematical model is presented which can simulate the major features of the interactions between ammonium and nitrate transport and assimilation in phytoplankton. The model (ammonium-nitrate interaction model), which is configured to simulate a generic microalga rather than a specified species, is constructed on simplified biochemical bases. A major requirement for parametrization is that the N:C ratio of the algae must be known and that transport and internal pool sizes need to be expressed per unit of cell C. The model uses the size of an internal pool of an early organic product of N assimilation (glutamine) to regulate rapid responses in ammonium-nitrate interactions. The synthesis of enzymes for the reduction of nitrate through to ammonium is induced by the size of the internal nitrate pool and repressed by the size of the glutamine pool. The assimilation of intracellular ammonium (into glutamine) is considered to be a constitutive process subjected to regulation by the size of the glutamine pool. Longer term responses have been linked to the nutrient history of the cell using the N:C cell quota. N assimilation in darkness is made a function of the amount of surplus C present and thus only occurs at low values of N:C. The model can simulate both qualitative and quantitative temporal shifts in the ammonium-nitrate interaction, while inclusion of a derivation of the standard quota model enables a concurrent simulation of cell growth and changes in nutrient status.

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21

Dähnke, K., A. Moneta, B. Veuger, K. Soetaert y J. J. Middelburg. "Nitrogen turnover in a tidal flat sediment: assimilation and dissimilation by bacteria and benthic microalgae". Biogeosciences Discussions 9, n.º 6 (14 de junio de 2012): 6987–7019. http://dx.doi.org/10.5194/bgd-9-6987-2012.

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Abstract. In a short-term (24 h) 15N-labeling experiment, we investigated reactive nitrogen cycling in a tidal flat sediment, focusing on the relative importance of assimilatory versus dissimilatory processes and the role of benthic microalgae therein. 15N-labeled ammonium and nitrate were added separately to homogenized sediment, and 15N was subsequently traced into sediment and dissolved inorganic nitrogen (DIN) pools. Integration of results in a N-cycle model allowed us to quantify rates for the major assimilatory and dissimilatory processes in the sediment. Overall, results indicate that the balance between assimilation and dissimilation in this tidal mudflat was mainly dependent on the nitrogen source. Nitrate was utilized almost exclusively dissimilatory via denitrification, whereas ammonium was rapidly assimilated, with about a quarter of this assimilation due to benthic microalgae (BMA). Benthic microalgae significantly affect assimilation of ammonium, because in the absence of BMA activity the sediments turns from a net ammonium sink to a net source. Nitrification rates were initially very high, but declined rapidly suggesting that nitrification rates are low in undisturbed sediments, and that in a dynamic environment like tidal flats, intense and fast nitrification/denitrification of ammonium is common. The driving mechanisms for assimilation or dissimilation accordingly appear to be ruled to a large extent by external physical forcing, with the entire system being capable of rapid shifts following environmental changes.

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22

Flores, E. y A. Herrero. "Nitrogen assimilation and nitrogen control in cyanobacteria". Biochemical Society Transactions 33, n.º 1 (1 de febrero de 2005): 164–67. http://dx.doi.org/10.1042/bst0330164.

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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.

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23

Hoque, Mohammad S., Josette Masle, Michael K. Udvardi, Peter R. Ryan y Narayana M. Upadhyaya. "Over-expression of the rice OsAMT1-1 gene increases ammonium uptake and content, but impairs growth and development of plants under high ammonium nutrition". Functional Plant Biology 33, n.º 2 (2006): 153. http://dx.doi.org/10.1071/fp05165.

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A transgenic approach was undertaken to investigate the role of a rice ammonium transporter (OsAMT1-1) in ammonium uptake and consequent ammonium assimilation under different nitrogen regimes. Transgenic lines overexpressing OsAMT1-1 were produced by Agrobacterium-mediated transformation of two rice cultivars, Taipei 309 and Jarrah, with an OsAMT1-1 cDNA gene construct driven by the maize ubiquitin promoter. Transcript levels of OsAMT1-1 in both Taipei 309 and Jarrah transgenic lines correlated positively with transgene copy number. Shoot and root biomass of some transgenic lines decreased during seedling and early vegetative stage compared to the wild type, especially when grown under high (2 mm) ammonium nutrition. Transgenic plants, particularly those of cv. Jarrah recovered in the mid-vegetative stage under high ammonium nutrition. Roots of the transgenic plants showed increased ammonium uptake and ammonium content. We conclude that the decreased biomass of the transgenic lines at early stages of growth might be caused by the accumulation of ammonium in the roots owing to the inability of ammonium assimilation to match the greater ammonium uptake.

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24

Wang, Rui, Shengjun Xu, Cancan Jiang, Haishu Sun, Shugeng Feng, Sining Zhou, Guoqiang Zhuang, Zhihui Bai y Xuliang Zhuang. "Transcriptomic Sequencing and Co-Expression Network Analysis on Key Genes and Pathways Regulating Nitrogen Use Efficiency in Myriophyllum aquaticum". International Journal of Molecular Sciences 20, n.º 7 (29 de marzo de 2019): 1587. http://dx.doi.org/10.3390/ijms20071587.

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Massively input and accumulated ammonium is one of the main causes of eutrophication in aquatic ecosystems, which severely deteriorates water quality. Previous studies showed that one of the commonly used macrophytes, Myriophyllum aquaticum, was capable of not only withstanding ammonium of high concentration, but also efficiently assimilating extracellular ammonium to constitutive amino acids and proteins. However, the genetic mechanism regulating such efficient nitrogen metabolism in M. aquaticum is still poorly understood. Therefore, RNA-based analysis was performed in this study to understand the ammonium regulatory mechanism in M. aquaticum in response to various concentrations of ammonium. A total of 7721 genes were differentially expressed, of which those related to nitrogen-transport, assimilation, and remobilization were highly-regulated in response to various concentrations of ammonium. We have also identified transcription factors and protein kinases that were rapidly induced in response to ammonium, which suggests their involvement in ammonium-mediated signalling. Meanwhile, secondary metabolism including phenolics and anthocyanins biosynthesis was also activated in response to various concentrations of ammonium, especially at high ammonium concentrations. These results proposed a complex physiological and genetic regulation network related to nitrogen, carbohydrate, transcription factors, and secondary metabolism for nitrogen use efficiency in M. aquaticum.

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25

Mathur, Malvika y S. N. Mathur. "Ammonium Assimilation in Leaf Tissues of Vigna mungo". Biochemie und Physiologie der Pflanzen 180, n.º 3 (enero de 1985): 247–50. http://dx.doi.org/10.1016/s0015-3796(85)80021-4.

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26

Ramazanov, Ziyadin y Jacobo Cardenas. "Photorespiratory ammonium assimilation in chloroplasts of Chlamydomonas reinhardtii". Physiologia Plantarum 91, n.º 3 (julio de 1994): 495–502. http://dx.doi.org/10.1034/j.1399-3054.1994.910320.x.

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27

Canovas, F. M., C. Avila, F. R. Canton, R. A. Canas y F. de la Torre. "Ammonium assimilation and amino acid metabolism in conifers". Journal of Experimental Botany 58, n.º 9 (9 de marzo de 2007): 2307–18. http://dx.doi.org/10.1093/jxb/erm051.

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28

Weger, Harold G., Douglas G. Birch, Ivor R. Elrifi y David H. Turpin. "Ammonium Assimilation Requires Mitochondrial Respiration in the Light". Plant Physiology 86, n.º 3 (1 de marzo de 1988): 688–92. http://dx.doi.org/10.1104/pp.86.3.688.

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29

AHMAD, IFTIKHAR y JOHAN A. HELLEBUST. "Enzymology of ammonium assimilation in three green flagellates". New Phytologist 109, n.º 4 (agosto de 1988): 415–21. http://dx.doi.org/10.1111/j.1469-8137.1988.tb03717.x.

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30

Ramazanov, Ziyadin y Jacobo Cardenas. "Photorespiratory ammonium assimilation in chloroplasts of Chlamydomonas reinhardtii". Physiologia Plantarum 91, n.º 3 (julio de 1994): 495–502. http://dx.doi.org/10.1111/j.1399-3054.1994.tb02979.x.

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31

Turnbull, MH, R. Goodall y GR Stewart. "Evaluating the Contribution of Glutamate Dehydrogenase and the Glutamate Synthase Cycle to Ammonia Assimilation by Four Ectomycorrhizal Fungal Isolates". Functional Plant Biology 23, n.º 2 (1996): 151. http://dx.doi.org/10.1071/pp9960151.

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Combined gas chromatography-mass spectrometry were used to evaluate the contributions of glutamate dehydrogenase (GDH) and the glutamate synthase cycle in 15N-labelled ammonium assimilation by four ectomycorrhizal fungal isolates. In all four species (Elaphomyces, Amanita, Pisolithus and Gautieria), glutamine was the major product accumulated following transfer of 14-day-old nitrogen-limited cultures to fresh medium. Label was rapidly assimilated into fungal tissue, with rates of 733 nmol g-1 FW h-1 in Pisolithus, 972 nmol g-1 FW h-1 in Amanita, 2760 nmol g-1 FW h-1 in Gautieria and 6756 nmol g-1 FW h-1 in Elaphomyces sp in the first 4 h of incubation. Incorporation of [15N]ammonium was sensitive to the inhibitory effects of both methionine sulfoximine (MSX, an inhibitor of glutamine synthetase (GS)) and albizziin (an inhibitor of glutamate synthase (GOGAT)) in three species (Amanita, Gautieria and Pisolithus) and labelling patterns were consistent with the action of the glutamate synthase cycle in ammonium assimilation. In all three species glutamine synthesis was almost totally blocked by MSX and there was no continued incorporation of 15N into glutamate. Elaphomyces displayed high levels of total incorporation of labelled ammonium in mycelium even in the presence of MSX, although incorporation into glutamine was reduced by 88%. This inhibition of GS by MSX, in addition to its partial inhibition by albizziin suggests strongly the action of glutamate synthase cycle in ammonium assimilation. The reduction in label entering glutamate under the influence of albizziin is direct evidence for the inhibition of GOGAT activity. However, MSX treatment had the effect of increasing significantly the quantity of label recovered in both glutamate and alanine. In the absence of GS inhibition there is clearly competition for ammonium which under normal physiological conditions results in assimilation through the glutamate synthase cycle. However, when GS is blocked by MSX label is able to cycle through the GDH pathway. Extra keywords: ectomycorrhiza, ammonium assimilation, glutamate synthase cycle, glutamate dehydrogenase, amino acid metabolism.

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32

Chávez, S., J. M. Lucena, J. C. Reyes, F. J. Florencio y P. Candau. "The Presence of Glutamate Dehydrogenase Is a Selective Advantage for the Cyanobacterium Synechocystis sp. Strain PCC 6803 under Nonexponential Growth Conditions". Journal of Bacteriology 181, n.º 3 (1 de febrero de 1999): 808–13. http://dx.doi.org/10.1128/jb.181.3.808-813.1999.

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ABSTRACT The unicellular cyanobacterium Synechocystis sp. strain PCC 6803 has two putative pathways for ammonium assimilation: the glutamine synthetase-glutamate synthase cycle, which is the main one and is finely regulated by the nitrogen source; and a high NADP-dependent glutamate dehydrogenase activity (NADP-GDH) whose contribution to glutamate synthesis is uncertain. To investigate the role of the latter, we used two engineered mutants, one lacking and another overproducing NADP-GDH. No major disturbances in the regulation of nitrogen-assimilating enzymes or in amino acids pools were detected in the null mutant, but phycobiline content, a sensitive indicator of the nutritional state of cyanobacterial cells, was significantly reduced, indicating that NADP-GDH plays an auxiliary role in ammonium assimilation. This effect was already prominent in the initial phase of growth, although differences in growth rate between the wild type and the mutants were observed at this stage only at low light intensities. However, the null mutant was unable to sustain growth at the late stage of the culture at the point when the wild type showed the maximum NADP-GDH activity, and died faster in ammonium-containing medium. Overexpression of NADP-GDH improved culture proliferation under moderate ammonium concentrations. Competition experiments between the wild type and the null mutant confirmed that the presence of NADP-GDH confers a selective advantage toSynechocystis sp. strain PCC 6803 in late stages of growth.

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33

Shapiro, S., L. C. Vining, M. Laycock, A. G. McInnes y J. A. Walter. "Pathway of ammonium assimilation in Streptomyces venezuelae examined by amino acid analyses and 15N nuclear magnetic resonance spectroscopy". Canadian Journal of Microbiology 31, n.º 7 (1 de julio de 1985): 629–34. http://dx.doi.org/10.1139/m85-119.

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To obtain information on the route(s) of ammonium assimilation in Streptomyces venezuelae, cell suspensions transferred to fresh medium lacking nitrogen were pulsed with [15N2]ammonium sulphate. Cells and extracellular fluids were examined by nuclear magnetic resonance and amino acid analysis to assess changes in amino acid pools and the disposition of [15N]ammonium. Following addition of [15N]ammonium, glutamate–glutamine pools of low cell density replacement cultures expanded rapidly and became progressively labelled with 15N, whereas the alanine pool size increased much more slowly and became labelled with 15N to a much lesser extent. These results are consistent with the assimilation of ammonium via glutamate dehydrogenase or glutamine synthetase – glutamate synthase rather than alanine dehydrogenase. Under anaerobic conditions, S. venezuelae assimilates ammonium into alanine rather than glutamate–glutamine. Alanine dehydrogenase may thus function as a vehicle to regenerate NAD+ to maintain substrate-level phosphorylation during periods of anaerobiosis.

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34

LeKieffre, Charlotte, Howard J. Spero, Jennifer S. Fehrenbacher, Ann D. Russell, Haojia Ren, Emmanuelle Geslin y Anders Meibom. "Ammonium is the preferred source of nitrogen for planktonic foraminifer and their dinoflagellate symbionts". Proceedings of the Royal Society B: Biological Sciences 287, n.º 1929 (17 de junio de 2020): 20200620. http://dx.doi.org/10.1098/rspb.2020.0620.

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The symbiotic planktonic foraminifera Orbulina universa inhabits open ocean oligotrophic ecosystems where dissolved nutrients are scarce and often limit biological productivity. It has previously been proposed that O. universa meets its nitrogen (N) requirements by preying on zooplankton, and that its symbiotic dinoflagellates recycle metabolic ‘waste ammonium’ for their N pool. However, these conclusions were derived from bulk 15 N-enrichment experiments and model calculations, and our understanding of N assimilation and exchange between the foraminifer host cell and its symbiotic dinoflagellates remains poorly constrained. Here, we present data from pulse-chase experiments with 13 C-enriched inorganic carbon, 15 N-nitrate, and 15 N-ammonium, as well as a 13 C- and 15 N- enriched heterotrophic food source, followed by TEM (transmission electron microscopy) coupled to NanoSIMS (nanoscale secondary ion mass spectrometry) isotopic imaging to visualize and quantify C and N assimilation and translocation in the symbiotic system. High levels of 15 N-labelling were observed in the dinoflagellates and in foraminiferal organelles and cytoplasm after incubation with 15 N-ammonium, indicating efficient ammonium assimilation. Only weak 15 N-assimilation was observed after incubation with 15 N-nitrate. Feeding foraminifers with 13 C- and 15 N-labelled food resulted in dinoflagellates that were labelled with 15 N, thereby confirming the transfer of 15 N-compounds from the digestive vacuoles of the foraminifer to the symbiotic dinoflagellates, likely through recycling of ammonium. These observations are important for N isotope-based palaeoceanographic reconstructions, as they show that δ 15 N values recorded in the organic matrix in symbiotic species likely reflect ammonium recycling rather than alternative N sources, such as nitrates.

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35

Miller, Scott R. y Richard W. Castenholz. "Ecological Physiology of Synechococcussp. Strain SH-94-5, a Naturally Occurring Cyanobacterium Deficient in Nitrate Assimilation". Applied and Environmental Microbiology 67, n.º 7 (1 de julio de 2001): 3002–9. http://dx.doi.org/10.1128/aem.67.7.3002-3009.2001.

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ABSTRACT Synechococcus sp. strain SH-94-5 is a nitrate assimilation-deficient cyanobacterium which was isolated from an ammonium-replete hot spring in central Oregon. While this clone could grow on ammonium and some forms of organic nitrogen as sole nitrogen sources, it could not grow on either nitrate or nitrite, even under conditions favoring passive diffusion. It was determined that this clone does not express functional nitrate reductase or nitrite reductase and that the lack of activity of either enzyme is not due to inactivation of the cyanobacterial nitrogen control protein NtcA. A few other naturally occurring cyanobacterial strains are also nitrate assimilation deficient, and phylogenetic analyses indicated that the ability to utilize nitrate has been independently lost at least four times during the evolutionary history of the cyanobacteria. This phenotype is associated with the presence of environmental ammonium, a negative regulator of nitrate assimilation gene expression, which may indicate that natural selection to maintain functional copies of nitrate assimilation genes has been relaxed in these habitats. These results suggest how the evolutionary fates of conditionally expressed genes might differ between environments and thereby effect ecological divergence and biogeographical structure in the microbial world.

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36

Younesi, O. y A. Moradi. "Effect of Salinity on Nodulation, Glutamine Synthetase and Glutamate Synthase Activity in Nodules of Alfalfa (Medicago sativa L.)". Cercetari Agronomice in Moldova 48, n.º 4 (1 de diciembre de 2015): 61–70. http://dx.doi.org/10.1515/cerce-2015-0053.

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Abstract Bami cultivar of alfalfa (Medicago sativa) was inoculated with salt-tolerant Sinorhizobium meliloti in solution culture with different salt concentrations (0, 50, 75 and 100 mmoles 1-1NaCl) added immediately at the time of inoculation. The results indicated that S. meliloti formed an infective and effective symbiosis with alfalfa under saline and nonsaline conditions. Salinity significantly decreased shoot and root dry weight, nodule weight and mean nodule weight. Roots were more sensitive than shoots, and N2 fixation was more sensitive to salinity than was plant growth. Analyses of ammonium assimilating enzymes in the nodule showed that glutamine synthetase appeared to be more tolerant to salinity than glutamate synthase, and that it limits ammonium assimilation under saline stress.

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37

Michel-Reydellet, Nathalie y P. Alexandre Kaminski. "Azorhizobium caulinodans PIIand GlnK Proteins Control Nitrogen Fixation and Ammonia Assimilation". Journal of Bacteriology 181, n.º 8 (15 de abril de 1999): 2655–58. http://dx.doi.org/10.1128/jb.181.8.2655-2658.1999.

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ABSTRACT We herein report that Azorhizobium caulinodansPII and GlnK are not necessary for glutamine synthetase (GS) adenylylation whereas both proteins are required for complete GS deadenylylation. The disruption of both glnB andglnK resulted in a high level of GS adenylylation under the condition of nitrogen fixation, leading to ammonium excretion in the free-living state. PII and GlnK also controllednif gene expression because NifA activated nifHtranscription and nitrogenase activity was derepressed in glnB glnK double mutants, but not in wild-type bacteria, grown in the presence of ammonia.

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38

Kojima, Soichi, Noriyuki Konishi, Marcel Pascal Beier, Keiki Ishiyama, Ikumi Maru, Toshihiko Hayakawa y Tomoyuki Yamaya. "NADH-dependent glutamate synthase participated in ammonium assimilation inArabidopsisroot". Plant Signaling & Behavior 9, n.º 8 (4 de junio de 2014): e29402. http://dx.doi.org/10.4161/psb.29402.

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39

LOMNITZ, A., J. CALDERON, G. HERNANDEZ y J. MORA. "Functional Analysis of Ammonium Assimilation Enzymes in Neurospora crassa". Microbiology 133, n.º 8 (1 de agosto de 1987): 2333–40. http://dx.doi.org/10.1099/00221287-133-8-2333.

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40

BRANA, A. F., N. PAIVA y A. L. DEMAIN. "Pathways and Regulation of Ammonium Assimilation in Streptomyces clavuligerus". Microbiology 132, n.º 5 (1 de mayo de 1986): 1305–17. http://dx.doi.org/10.1099/00221287-132-5-1305.

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41

Tobin, Alyson K. y Tomoyuki Yamaya. "Cellular compartmentation of ammonium assimilation in rice and barley". Journal of Experimental Botany 52, n.º 356 (abril de 2001): 591–604. http://dx.doi.org/10.1093/jexbot/52.356.591.

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42

Arnozis, P. A. y A. J. Barneix. "Pep‐carboxylase activity during ammonium‐assimilation in wheat plants". Journal of Plant Nutrition 12, n.º 1 (enero de 1989): 85–94. http://dx.doi.org/10.1080/01904168909363937.

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43

RAVEN, J. A. y M. I. MICHELIS. "Acid-base regulation during ammonium assimilation in Hydrodictyon africanum". Plant, Cell & Environment 3, n.º 5 (28 de abril de 2006): 325–38. http://dx.doi.org/10.1111/1365-3040.ep11581869.

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44

Tobin, Alyson K. y Tomoyuki Yamaya. "Cellular compartmentation of ammonium assimilation in rice and barley". Journal of Experimental Botany 52, n.º 356 (abril de 2001): 591–604. http://dx.doi.org/10.1093/jxb/52.356.591.

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45

HIPKIN, C. R., K. J. FLYNN, E. MARJOT, Z. S. HAMOUDI y A. C. CANNONS. "Ammonium assimilation by the nitrate-utilizing yeast, Candida nitratophila". New Phytologist 114, n.º 3 (marzo de 1990): 429–34. http://dx.doi.org/10.1111/j.1469-8137.1990.tb00410.x.

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46

Ferousi, Christina, Simon Lindhoud, Frauke Baymann, Boran Kartal, Mike SM Jetten y Joachim Reimann. "Iron assimilation and utilization in anaerobic ammonium oxidizing bacteria". Current Opinion in Chemical Biology 37 (abril de 2017): 129–36. http://dx.doi.org/10.1016/j.cbpa.2017.03.009.

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47

Baars, Johan J. P., Huub J. M. Op den Camp, Chris van der Drift, Jos J. M. Joordens, Sybren S. Wijmenga, Leo J. L. D. van Griensven y Godfried D. Vogels. "15N-NMR study of ammonium assimilation in Agaricus bisporus". Biochimica et Biophysica Acta (BBA) - Molecular Cell Research 1310, n.º 1 (enero de 1996): 74–80. http://dx.doi.org/10.1016/0167-4889(95)00157-3.

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48

Caballero, Antonio, Abraham Esteve-Núñez, Gerben J. Zylstra y Juan L. Ramos. "Assimilation of Nitrogen from Nitrite and Trinitrotoluene in Pseudomonas putida JLR11". Journal of Bacteriology 187, n.º 1 (1 de enero de 2005): 396–99. http://dx.doi.org/10.1128/jb.187.1.396-399.2005.

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ABSTRACT Pseudomonas putida JLR11 releases nitrogen from the 2,4,6-trinitrotoluene (TNT) ring as nitrite or ammonium. These processes can occur simultaneously, as shown by the observation that a nasB mutant impaired in the reduction of nitrite to ammonium grew at a slower rate than the parental strain. Nitrogen from TNT is assimilated via the glutamine syntethase-glutamate synthase (GS-GOGAT) pathway, as evidenced by the inability of GOGAT mutants to use TNT. This pathway is also used to assimilate ammonium from reduced nitrate and nitrite. Three mutants that had insertions in ntrC, nasT, and cnmA, which encode regulatory proteins, failed to grow on nitrite but grew on TNT, although slower than the wild type.

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49

Taté, Rosarita, Anna Riccio, Mike Merrick y Eduardo J. Patriarca. "The Rhizobium etli amtB Gene Coding for an NH4+ Transporter Is Down-Regulated Early During Bacteroid Differentiation". Molecular Plant-Microbe Interactions® 11, n.º 3 (marzo de 1998): 188–98. http://dx.doi.org/10.1094/mpmi.1998.11.3.188.

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During development of root nodules, Rhizobium bacteria differentiate inside the invaded plant cells into N2-fixing bacteroids. Terminally differentiated bacteroids are unable to grow using the ammonia (NH3 ) produced therein by the nitrogenase complex. Therefore, the nitrogen assimilation activities of bacteroids, including the ammonium (NH4 +) uptake activity, are expected to be repressed during symbiosis. By sequence homology the R. etli amtB (ammonium transport) gene was cloned and sequenced. As previously shown for its counterpart in other organisms, the R. etli amtB gene product mediates the transport of NH4 +. The amtB gene is cotranscribed with the glnK gene (coding for a PII-like protein) from a nitrogen-regulated σ54-dependent promoter, which requires the transcriptional activator NtrC. Expression of the glnKamtB operon was found to be activated under nitrogen-limiting, free-living conditions, but down-regulated just when bacteria are released from the infection threads and before transcription of the nitrogenase genes. Our data suggest that the uncoupling between N2-fixation and NH3 assimilation observed in symbiosomes is generated by a transcriptional regulatory mechanism(s) beginning with the inactivation of NtrC in younger bacteroids.

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50

Burzyński, Marek y Józef Buczek. "Uptake and assimilation of ammonium ions by cucumber seedlings from solutions with different pH and addition of heavy metals". Acta Societatis Botanicorum Poloniae 67, n.º 2 (2014): 197–200. http://dx.doi.org/10.5586/asbp.1998.023.

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Influence of Cu2+, Cd2+, Pb2+ and Fe2+ in various pH conditions (5.0, 6.0, 7.0) on the uptake and assimilation of NH4+ by cucumber seedlings was estimated. Every metal in different pH of uptake solution distinctly reduced ammonium absorption calculated from NH4+ depletion. Copper and ferric ions, but not cadmium or lead, astonishingly decreased the uptake of ammonium from solution at pH 5.0. Cu2+ was also very active at pH 6.0. The accumulation of ammonium in roots of metals-treated seedlings at the same time was high. The high level of ammonium in root cells despite of its low uptake probably resulted from disturbance in NH4+ assimilation. Both glutamine synthetase (GS) and NADH-glutamate dehydrogenase (NADH-GDH) - the major enzymes in ammonium assimilation, were inhibited after one hour of plant exposition to the metals. Similarly as in the case of ammonium uptake, the influence of pH was visible only in combination with copper and ferric ions. The strongest reduction of enzyme activities was observed for Cu2+ and Fe2+, in pH 5.0 and 6.0. The various metals absorption by roots from solutions with different pH was not dedected. The data show correlation between metal inhibition of GS and NADH-GDH activities and metal inhibition of ammonium absorption.

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