Journal articles: 'Nitroge fixation'

1

Peng, Peng, Paul Chen, Min Addy, Yanling Cheng, Yaning Zhang, Erik Anderson, Nan Zhou, et al. "In situ plasma-assisted atmospheric nitrogen fixation using water and spray-type jet plasma." Chemical Communications 54, no. 23 (2018): 2886–89. http://dx.doi.org/10.1039/c8cc00697k.

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Nagiev, T. M., N. I. Ali-zadeh, L. M. Gasanova, I. T. Nagieva, Ch A. Mustafaeva, N. N. Malikova, A. A. Abdullaeva, and E. S. Bakhramov. "NITROGEN FIXATION AT CONJUGATED OXIDATION." Azerbaijan Chemical Journal, no. 2 (2018): 6–10. http://dx.doi.org/10.32737/0005-2531-2018-2-6-10.

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Flores, E., and A. Herrero. "Nitrogen assimilation and nitrogen control in cyanobacteria." Biochemical Society Transactions 33, no. 1 (February 1, 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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Madinger, Hilary L., and Robert O. Hall Jr. "Nitrogen fluxes in Western streams." UW National Parks Service Research Station Annual Reports 40 (December 15, 2017): 61–68. http://dx.doi.org/10.13001/uwnpsrc.2017.5575.

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Nitrogen pollution to streams is altering the nitrogen cycling in unknown ways, causing challenges for predicting nitrogen fixation fluxes within aquatic ecosystems. Increasing nitrate pollution decreases the amount of nitrogen fixation occurring in streams. However, the relationship between stream nitrate concentration and the rate of nitrogen fixation is unknown. We predict that lower nitrate streams will have the highest rates of nitrogen fixation. Additionally, there will be much more energy produced in streams with nitrogen fixation compared to the amount required to fix the nitrogen. We estimated whole-stream gross primary production and nitrogen fixation fluxes using the diel change in dissolved nitrogen and oxygen gases compared to the expected dissolved gas saturation. Our whole-stream method is preferable to chamber estimates to understand the relationship between energy requirements for nitrogen fixation and gross primary production, but additional data is needed to distinguish between relationship types and make our measurements generalizable. Featured photo by Intermountain Forest Service, USDA Region 4 Photography on Flickr. https://flic.kr/p/jbTRUj

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Herridge, D. F., J. E. Turpin, and M. J. Robertson. "Improving nitrogen fixation of crop legumes through breeding and agronomic management: analysis with simulation modelling." Australian Journal of Experimental Agriculture 41, no. 3 (2001): 391. http://dx.doi.org/10.1071/ea00041.

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The nitrogen fixed by legumes is a valuable resource in agriculture, with crop legumes alone contributing as much as 20% of the nitrogen requirements of the world’s grain and oilseed crops. Increasing legume nitrogen fixation through genetic improvement and more efficient management would have large economic benefits. Breeding for improved nitrogen fixation has, to a large extent, not been successful. Suggested reasons include the difficulty in combining single traits like nitrogen fixation with other traits, such as disease resistance, seed quality and yield, a lack of focus of programs and a lack of screening methodologies. Agronomic management of legume nitrogen fixation offers other opportunities. The challenge is to package those opportunities and provide legume growers with tools for understanding the factors determining nitrogen fixation, while at the same time providing them with site-specific management options. The potential of simulation modelling for assessing genetic and management options for enhancing nitrogen fixation of soybean grown at Warwick in south-eastern Queensland was investigated in a series of 30-year simulations using the APSIM modelling framework. The APSIM–soybean module was first adjusted to reflect observed responses of nitrogen fixation to soil nitrate. The subsequent simulations indicated that (genetically based) symbiotic nitrate tolerance would have only marginal benefits on residual soil nitrate (7 kg N/ha at sowing soil nitrate of 100 kg N/ha). Management of the crop for highest grain yield through optimising sowing dates, plant density and fallow length provided the best opportunities for increasing nitrogen fixation. The use of APSIM as a tool for managing legume nitrogen fixation appears to have merit.

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Cejudo, F. J., and A. Paneque. "Short-term nitrate (nitrite) inhibition of nitrogen fixation in Azotobacter chroococcum." Journal of Bacteriology 165, no. 1 (1986): 240–43. http://dx.doi.org/10.1128/jb.165.1.240-243.1986.

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Sumaira Mazhar, Sumaira Mazhar, and Jerry D. Cohen and Shahida Hasnain Jerry D Cohen and Shahida Hasnain. "Novel Approach for the Determination of Nitrogen Fixation in Cyanobacteria." Journal of the chemical society of pakistan 41, no. 1 (2019): 105. http://dx.doi.org/10.52568/000711/jcsp/41.01.2019.

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Non-heterocystous nitrogen fixing strains of cyanobacteria were screened by their ability to grow in nitrogen deficient media. The selected nitrogen fixing cyanobacterial cells were then cultured in BG11 media supplemented with [15N]-labeled sodium nitrate. Under these growth conditions any organic [14N] found in the cyanobacterial cells would simply come from nitrogen fixation because [15N] was the only available source of nitrogen in the medium. Amino acids extracted after different time periods (after 15, 30, 40, 50 and 60 days of inoculation) were used for the determination of the 14N/15N ratio using GC-MS. Results from the present study support the conclusion that at stationary phase of growth cyanobacterial nitrogen fixation was no longer supplying a significant amount of nitrogen. This approach not only provided a detailed method for the evaluation of the nitrogen fixing potential of the cyanobacteria in culture, but also suggests novel approaches for the assessment of the ability of the strains to provide nitrogen enrichment to plants under co-cultivation conditions.

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Moreira-Coello, Víctor, Beatriz Mouriño-Carballido, Emilio Marañón, Ana Fernández-Carrera, María PÉrez-Lorenzo, and Antonio Bode. "Quantifying the overestimation of planktonic N2 fixation due to contamination of 15N2 gas stocks." Journal of Plankton Research 41, no. 4 (July 2019): 567–70. http://dx.doi.org/10.1093/plankt/fbz034.

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AbstractThe 15N2-tracer assay [Montoya et al. (1996) A simple, high-precision, high-sensitivity tracer assay for N2 fixation. Appl. Environ. Microbiol., 62, 986–993.] is the most used method for measuring biological N2 fixation in terrestrial and aquatic environments. The reliability of this technique depends on the purity of the commercial 15N2 gas stocks used. However, Dabundo et al. [(2014) PLoS One, 9, e110335.] reported the contamination of some of these stocks with labile 15N-labeled compounds (ammonium, nitrate and/or nitrite). The contamination of commercial 15N2 gas stocks with 15N-labeled nitrate and 142 ammonium and consequences for nitrogen fixation measurements. Considering that the tracer assay relies on the conversion of isotopically labeled 15N2 into organic nitrogen, this contamination may have led to overestimated N2 fixation rates. We conducted laboratory and field experiments in order to (i) test the susceptibility of 15N contaminants to assimilation by non-diazotroph organisms and (ii) determine the potential overestimation of the N2 fixation rates estimated in the field. Our findings indicate that the contaminant 15N-compounds are assimilated by non-diazotrophs organisms, leading to an overestimation of N2 fixation rates in the field up to 16-fold under hydrographic conditions of winter mixing.

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Shiozaki, T., T. Nagata, M. Ijichi, and K. Furuya. "Seasonal dynamics of nitrogen fixation and the diazotroph community in the temperate coastal region of the northwestern North Pacific." Biogeosciences Discussions 12, no. 1 (January 15, 2015): 865–89. http://dx.doi.org/10.5194/bgd-12-865-2015.

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Abstract. Nitrogen fixation in temperate oceans is a potentially important, but poorly understood process that may influence the marine nitrogen budget. This study determined seasonal variations in nitrogen fixation and nifH gene diversity within the euphotic zone in the temperate coastal region of the northwestern North Pacific. Nitrogen fixation as high as 13.6 nmolN L−1 d−1 was measured from early summer to fall when the surface temperature exceeded 14.2 °C and the surface nitrate concentration was low (≤ 0.30 μM), although we also detected nitrogen fixation in subsurface layers (42–62 m) where nitrate concentrations were high (> 1 μM). During periods with high nitrogen fixation, the nifH sequences of UCYN-A were recovered, suggesting that these groups played a key role in nitrogen fixation. The nifH genes were also recovered in spring and winter when nitrogen fixation was undetectable. These genes consisted of many sequences affiliated with Cluster III diazotrophs (putative anaerobic bacteria), which hitherto have rarely been reported to be abundant in surface diazotroph communities in marine environments.

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McFarland, Mel A., and Dale W. Toetz. "Nitrogen fixation (acetylene reduction) in Lake Hefner, Oklahoma." Archiv für Hydrobiologie 114, no. 2 (December 14, 1988): 213–30. http://dx.doi.org/10.1127/archiv-hydrobiol/114/1988/213.

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OBI, A. OLU, R. A. HEDLIN, and C. M. CHO. "CROP UTILIZATION AND SOIL RETENTION OF NITROGEN FROM 15N-LABELLED UREA, CALCIUM NITRATE, and AMMONIUM SULPHATE IN SEVERAL MANITOBA SOILS." Canadian Journal of Soil Science 66, no. 4 (November 1, 1986): 661–71. http://dx.doi.org/10.4141/cjss86-066.

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A growth chamber study was carried out to determine crop utilization of nitrogen added as 15N-labelled calcium nitrate or urea to eight Manitoba soils of diverse characteristics. Dry matter yield of wheat was significantly greater where calcium nitrate was used as a nitrogen source than when urea was the nitrogen source in Pine Ridge, Wellwood, and Granville soils. Residual nitrogen in the soil at the end of the experiment was greater where urea was used than where calcium nitrate was used. Total recovery of urea nitrogen generally exceeded recovery of nitrogen from calcium nitrate. In a laboratory study it was found that more of the nitrogen added as urea or ammonium sulphate was retained than when nitrogen added was as calcium nitrate. Rapid ammonium fixation from ammonium-yielding carriers occurred, especially in the Granville and Waitville soils. Ammonium fixation could be one reason for the higher utilization of nitrogen from nitrate than from ammonium sources. Key words: Nitrogen availability, ammonia-soil interaction

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Shiozaki, T., T. Nagata, M. Ijichi, and K. Furuya. "Nitrogen fixation and the diazotroph community in the temperate coastal region of the northwestern North Pacific." Biogeosciences 12, no. 15 (August 7, 2015): 4751–64. http://dx.doi.org/10.5194/bg-12-4751-2015.

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Abstract. Nitrogen fixation in temperate oceans is a potentially important, but poorly understood process that may influence the marine nitrogen budget. This study determined seasonal variations in nitrogen fixation and the diazotroph community within the euphotic zone in the temperate coastal region of the northwestern North Pacific. Nitrogen fixation as high as 13.6 nmol N L−1 d−1 was measured from early summer to fall when the surface temperature exceeded 14.2 °C (but was lower than 24.3 °C) and the surface nitrate concentration was low (≤ 0.30 μM), although we also detected nitrogen fixation in subsurface layers (42–62 m) where nitrate concentrations were high (> 1 μM). Clone library analysis results indicated that nifH gene sequences were omnipresent throughout the investigation period. During the period when nitrogen fixation was detected (early summer to fall), the genes affiliated with UCYN-A, Trichodesmium, and γ-proteobacterial phylotype γ-24774A11 were frequently recovered. In contrast, when nitrogen fixation was undetectable (winter to spring), many sequences affiliated with Cluster III diazotrophs (putative anaerobic bacteria) were recovered. Quantitative PCR analysis revealed that UCYN-A was relatively abundant from early to late summer compared with Trichodesmium and γ-24774A11, whereas Trichodesmium abundance was the highest among the three groups during fall.

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13

Takahashi, Mikio, and Yatsuka Saijo. "Nitrogen metabolism in Lake Kizaki, Japan V. The role of nitrogen fixation in nitrogen requirement of phytoplankton." Archiv für Hydrobiologie 112, no. 1 (March 24, 1988): 43–54. http://dx.doi.org/10.1127/archiv-hydrobiol/112/1988/43.

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14

Šimon, T. "Utilization of the biological nitrogen fixation for soil evaluation." Plant, Soil and Environment 49, No. 8 (December 10, 2011): 359–63. http://dx.doi.org/10.17221/4137-pse.

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Non-symbiotic nitrogen fixation (potential nitrogenase activity – PNA) of soil samples originating from different plots of long-term field experiments (selected variants: Nil, NPK [mineral fertilisation: 64.6–100 kg N/ha/year], FYM [farmyard manure], and FYM + NPK from three blocks III, IV and B with different crop rotation) was determined in laboratory experiments. The symbiotic nitrogen fixation (total nitrogenase activity – TNA) of the same soil samples was evaluated in hydroponic experiments with pea (2001, 2002) and lucerne (2001) in which the soil samples were used as a natural inoculum. The high values of PNA were found in the variants fertilised with FYM in all three blocks and all experiments. Simultaneously, the variants fertilised with mineral NPK reached low values of PNA. The farmyard manuring enhanced the number of free-living bacteria Azotobacter spp. that were identified in all soil samples. In the hydroponic experiments with pea, the highest nonsignificant values of TNA were found in variants B 284 (FYM + NPK) and III 254 (FYM + NPK) in 2001, and B 214 (FYM) and III 214 (FYM) in 2002. Plants inoculated with soil from these variants formed also high amounts of nodules (significant differences in block IV in 2001) and plant biomass. In the experiments with lucerne, the nonsignificantly highest TNA values were found in variant III 154 (NPK). Variants from block III (214, 254) and IV (114 and 154) showed the nonsignificantly lowest TNA values. The rhizobia that effectuate symbiosis with pea were more active in the soil samples in 2001 than those forming nodules on lucerne.

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Telling, J., M. Stibal, A. M. Anesio, M. Tranter, I. Nias, J. Cook, G. Lis, et al. "Microbial nitrogen cycling on the Greenland Ice Sheet." Biogeosciences Discussions 8, no. 5 (October 25, 2011): 10423–57. http://dx.doi.org/10.5194/bgd-8-10423-2011.

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Abstract. Microbial nitrogen cycling was investigated along a 79 km transect into the Greenland Ice Sheet (GrIS) in early August 2010. The depletion of dissolved nitrate and production of ammonium (relative to icemelt) in cryoconite holes within 7.5 km of the ice sheet margin suggested microbial uptake and ammonification respectively. Nitrogen fixation (<4.2 μmoles C2H4 m−2 day−1 to 16.3 μmoles C2H4 m−2 day−1) was active in some cryoconite holes at sites up to 5.7 km from the ice sheet margin, with nitrogen fixation inversely correlated to concentrations of inorganic nitrogen. There may be the potential for the zone of nitrogen fixation to progressively extend further into the interior of the GrIS as the melt season progresses as reserves of available nitrogen are depleted. Estimated annual inputs of nitrogen from nitrogen fixation along the transect were at least two orders of magnitude lower than inputs from precipitation, with the exception of a 100 m long marginal debris-rich zone where nitrogen fixation could potentially equal or exceed that of precipitation. The average estimated contribution of nitrogen fixation to the nitrogen demand of net microbial growth at sites along the transect ranged from 0% to 17.5%.

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Volkogon, V. V., O. I. Bakun, E. I. Volkogon, N. P. Shtanko, and P. G. Dulnev. "THE INFLUENCE OF TRIMAN-1 ON ASSOCIATIVE NITROGEN FIXATION AND NITROGEN FIXING MICROORGANISMS IN BARLEY ROOT ZONE." Agriciltural microbiology 6 (February 20, 2008): 29–38. http://dx.doi.org/10.35868/1997-3004.6.29-38.

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The influence of plant growth regulator triman-1 on nitrogen fixing bacteria and nitrogen fixation process in barley root zone was studied in the laboratory and field conditions. It was shown that triman- 1 enhances associative nitrogen fixation activity when mineral nitrogen fertilizers (N30) was used. The use of triman-1 increases efficiency of associative symbiosis more effectively with the use of carboammonium salts rather than with ammonium nitrate.

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Ma, Zili, Jianhong Chen, Dongbao Luo, Thomas Thersleff, Richard Dronskowski, and Adam Slabon. "Structural evolution of CrN nanocube electrocatalysts during nitrogen reduction reaction." Nanoscale 12, no. 37 (2020): 19276–83. http://dx.doi.org/10.1039/d0nr04981f.

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Liengen, Turid. "Environmental factors influencing the nitrogen fixation activity of free-living terrestrial cyanobacteria from a high arctic area, Spitsbergen." Canadian Journal of Microbiology 45, no. 7 (August 1, 1999): 573–81. http://dx.doi.org/10.1139/w99-040.

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The influence of environmental factors on the nitrogen fixation activity of free-living, terrestrial cyanobacteria from a high arctic area were investigated using experimental manipulations with two different types of field samples, including macroscopic sheets of Nostoc commune and soil samples with a cyanobacterial crust from a Puccinellia salt marsh. In addition, a cultured Anabaena sp. previously isolated from the salt marsh was examined. Nitrogen fixation activity was measured using the acetylene reduction method. The nitrogen fixation mainly took place in the light, but even after 12 h incubation in darkness, low activities were maintained. Phosphorus fertilization stimulated the nitrogen fixation activity, and the highest activities were obtained with about 300 μM phosphate, both in the field samples and the cultured Anabaena sp. Ammonium (28 mM) immediately inhibited the nitrogen fixation activity of the cultured Anabaena sp, whereas 14 mM urea and 540 μM glutamate led to a weaker and slower inhibition of the nitrogen fixation activity, showing that the cultured Anabaena sp. was able to assimilate these combined nitrogen sources. Nitrate did not have any inhibitory effect on nitrogen fixation activity, either in the field samples or in the cultured Anabaena sp. Both the field samples and the cultured Anabaena sp. showed tolerance against sodium chloride concentrations corresponding to the concentration in seawater. The temperature optimum of the nitrogen fixation activity of the cultured Anabaena sp. was about 20°C. Key words: nitrogen fixation, cyanobacteria, Nostoc commune, Anabaena sp., high arctic.

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Ding, Changling, Chao Wu, Congcong Guo, Jiang Gui, Yuqiu Wei, and Jun Sun. "The Composition and Primary Metabolic Potential of Microbial Communities Inhabiting the Surface Water in the Equatorial Eastern Indian Ocean." Biology 10, no. 3 (March 22, 2021): 248. http://dx.doi.org/10.3390/biology10030248.

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Currently, there is scant information about the biodiversity and functional diversity of microbes in the eastern Indian Ocean (EIO). Here, we used a combination of high-throughput sequencing of 16S rRNA genes and a metagenomic approach to investigate the microbial population structure and its metabolic function in the equatorial EIO. Our results show that Cyanobacterial Prochlorococcus made up the majority of the population. Interestingly, there were fewer contributions from clades SAR11 (Alphaproteobacteria) and SAR86 (Gammaproteobacteria) to microbial communities than contributions from Prochlorococcus. Based on functional gene analysis, functional genes rbcL, narB, and nasA were relatively abundant among the relevant genes. The abundance of Prochlorococcus implies its typically ecological adaptation in the local ecosystem. The microbial metabolic potential shows that in addition to the main carbon fixation pathway Calvin cycle, the rTCA cycle and the 3-HP/4-HB cycle have potential alternative carbon fixation contributions to local ecosystems. For the nitrogen cycle, the assimilatory nitrate and nitrite reduction pathway is potentially the crucial form of nitrogen utilization; unexpectedly, nitrogen fixation activity was relatively weak. This study extends our knowledge of the roles of microbes in energy and resource cycling in the EIO and provides a foundation for revealing profound biogeochemical processes driven by the microbial community in the ocean.

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Bednarz, J., and G. H. Schmid. "Further Studies on the Induction of Nitrate Reductase by Arginine in the Filamentous Cyanobacterium Oscillatoria chalybea." Zeitschrift für Naturforschung C 47, no. 7-8 (August 1, 1992): 540–44. http://dx.doi.org/10.1515/znc-1992-7-809.

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In an earlier publication we reported on the role of arginine for the development of nitrate reductase activity in cells of the filamentous cyanobacterium Oscillatoria chalybea (Bednarz and Schmid, Z. Naturforsch. 46c, 591 (1991)). In the present paper we present further evidence that arginine is the natural inducer for nitrate reductase activity. Thus, we show that the induction is regulated by transcription, probably related to the apoprotein or the molybdenumcofactor. We also examined the influence of arginine on nitrate reductase activity in the filamentous cyanobacterium Anabaena PCC7120. In contrast to Oscillatoria chalybea this cyanobacterium forms heterocysts and shows nitrogen fixation activity. Like in Oscillatoria chalybea nitrate reductase activity in Anabaena PCC7120 is stimulated in the presence of arginine as the sole nitrogen source. However, this stimulation is limited to an early growth stage. Subsequently, nitrogen fixation activity appears and nitrate reductase activity decreases.

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Summers, David P., and Bishun Khare. "Nitrogen Fixation on Early Mars and Other Terrestrial Planets: Experimental Demonstration of Abiotic Fixation Reactions to Nitrite and Nitrate." Astrobiology 7, no. 2 (April 2007): 333–41. http://dx.doi.org/10.1089/ast.2006.0032.

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Telling, J., M. Stibal, A. M. Anesio, M. Tranter, I. Nias, J. Cook, C. Bellas, et al. "Microbial nitrogen cycling on the Greenland Ice Sheet." Biogeosciences 9, no. 7 (July 5, 2012): 2431–42. http://dx.doi.org/10.5194/bg-9-2431-2012.

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Abstract. Nitrogen inputs and microbial nitrogen cycling were investigated along a 79 km transect into the Greenland Ice Sheet (GrIS) during the main ablation season in summer 2010. The depletion of dissolved nitrate and production of ammonium (relative to icemelt) in cryoconite holes on Leverett Glacier, within 7.5 km of the ice sheet margin, suggested microbial uptake and ammonification respectively. Positive in situ acetylene assays indicated nitrogen fixation both in a debris-rich 100 m marginal zone and up to 5.7 km upslope on Leverett Glacier (with rates up to 16.3 μmoles C2H4 m−2 day−1). No positive acetylene assays were detected > 5.7 km into the ablation zone of the ice sheet. Potential nitrogen fixation only occurred when concentrations of dissolved and sediment-bound inorganic nitrogen were undetectable. Estimates of nitrogen fluxes onto the transect suggest that nitrogen fixation is likely of minor importance to the overall nitrogen budget of Leverett Glacier and of negligible importance to the nitrogen budget on the main ice sheet itself. Nitrogen fixation is however potentially important as a source of nitrogen to microbial communities in the debris-rich marginal zone close to the terminus of the glacier, where nitrogen fixation may aid the colonization of subglacial and moraine-derived debris.

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Gandhi, Naveen, R. Ramesh, R. Srivastava, M. S. Sheshshayee, R. M. Dwivedi, and Mini Raman. "Nitrogen Uptake Rates during Spring in the NE Arabian Sea." International Journal of Oceanography 2010 (October 20, 2010): 1–10. http://dx.doi.org/10.1155/2010/127493.

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We present new data on N uptake rates and f-ratios in the north-eastern (NE) Arabian Sea, where significant amounts of Trichodesmium were present in spring, 2006. The measured total nitrogen uptake rates ranged from 0.34 to 1.58 mmol N . fixation associated with Trichodesmium varied from 0.002 to 0.54 mmol N estimated from the abundance of Trichodesmium and specific fixation rates of 1.5 pmol N trichome. Inclusion of fixation rates significantly changes f-ratios particularly in the coastal stations. Nitrogen isotopic data of surface suspended particles suggest that recently fixed nitrogen contributes as high as ~79% of the nitrogen in surface suspended particles. In addition, water column gained ~30 mmol N in the form of nitrate, likely due to nitrification of ammonium released by Trichodesmium. For better estimations, direct measurement of fixation is recommended.

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Bader, Klaus P., and Anja Röben. "Mass Spectrometric Detection and Analysis of Nitrogen Fixation in Oscillatoria chalybea." Zeitschrift für Naturforschung C 50, no. 3-4 (April 1, 1995): 199–204. http://dx.doi.org/10.1515/znc-1995-3-407.

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By means of mass spectroscopic measurements in an artifical gas atmosphere containing the stable nitrogen isotope 15N2 we were able to demonstrate nitrogen fixation capacity in the filamentous cyanobacterium Oscillatoria chalybea. Our technique proved to be wellsuited also for investigations on the light-induced nitrogen fixation in the purple bacteria Rhodobacter sphaeroides and Rhodobacter capsulatus. Oscillatoria chalybea grown without combined nitrogen showed a substantial 15N2-uptake which could clearly be correlated with nitrogen fixation. Nitrate grown cultures did not show this nitrogen uptake or only to a minimal extent. Addition of ammonium chloride resulted in a rapid deactivation of the nitrogenase system. Similar observations have been made with other so-called switch-off effectors like phenazine methosulfate. The structural integrity of the filaments appeared to be a prerequisite for nitrogen fixation also in this organism, as even mild mechanical homogenization strongly inhibited the N2-uptake signals. Illumination of the assays under conditions where the photooxidition of water is not operational (Bader, K. P. (1994), Biochim. Biophys. Acta 1188, 213 -219) did not affect the nitrogen fixation in Oscillatoria chalybea. Illumination of cultures with concomitant release of oxygen from the water splitting reaction resulted in strong inhibition of 15N2-uptake.

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Thompson, Niklas B., Michael T. Green, and Jonas C. Peters. "Nitrogen Fixation via a Terminal Fe(IV) Nitride." Journal of the American Chemical Society 139, no. 43 (October 19, 2017): 15312–15. http://dx.doi.org/10.1021/jacs.7b09364.

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B�hme, Herbert. "Inhibition of nitrogen fixation by nitrite inAnabaena variabilis." Archives of Microbiology 146, no. 1 (October 1986): 99–103. http://dx.doi.org/10.1007/bf00690166.

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Knapp, Angela N., Kelly M. McCabe, Olivier Grosso, Nathalie Leblond, Thierry Moutin, and Sophie Bonnet. "Distribution and rates of nitrogen fixation in the western tropical South Pacific Ocean constrained by nitrogen isotope budgets." Biogeosciences 15, no. 9 (May 4, 2018): 2619–28. http://dx.doi.org/10.5194/bg-15-2619-2018.

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Abstract. Constraining the rates and spatial distribution of dinitrogen (N2) fixation fluxes to the ocean informs our understanding of the environmental sensitivities of N2 fixation as well as the timescale over which the fluxes of nitrogen (N) to and from the ocean may respond to each other. Here we quantify rates of N2 fixation as well as its contribution to export production along a zonal transect in the western tropical South Pacific (WTSP) Ocean using N isotope (“δ15N”) budgets. Comparing measurements of water column nitrate + nitrite δ15N with the δ15N of sinking particulate N at a western, central, and eastern station, these δ15N budgets indicate high, modest, and low rates of N2 fixation at the respective stations. The results also imply that N2 fixation supports exceptionally high, i.e. ≥ 50 %, of export production at the western and central stations, which are also proximal to the largest iron sources. These geochemically based rates of N2 fixation are equal to or greater than those previously reported in the tropical North Atlantic, indicating that the WTSP Ocean has the capacity to support globally significant rates of N2 fixation, which may compensate for N removal in the oxygen-deficient zones of the eastern tropical Pacific.

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Silsbury, JH, DW Catchpoole, and W. Wallace. "Effects of Nitrate and Ammonium on Nitrogenase (C2H2 Reduction) Activity of Swards of Subterranean Clover, Trifolium subterraneum L." Functional Plant Biology 13, no. 2 (1986): 257. http://dx.doi.org/10.1071/pp9860257.

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Small swards of subterranean clover plants were grown under controlled conditions without mineral nitrogen and allowed to establish an effective nitrogen fixation system. Nutrient solutions containing nitrate from 0 to 16 mM or of ammonium from 0 to 5 mM were then applied and changes in nitrogenase activity (NA) estimated by acetylene reduction assay (AR) and the rate of hydrogen evolution (HE) for periods of up to 35 days. In two experiments a split-root system was used to enable mineral nitrogen to be applied to only one-half of a nodulated root system whilst the NA of both halves was monitored. NA by subterranean clover was very sensitive to exogenous mineral nitrogen, concentrations as low as 0.5 mM NO3- suppressing activity significantly, and 3-5 mM stopping it almost completely within 7 days. The degree of inhibition induced by concentrations between 0.5 and 3 mM NO3- was less at a photon irradiance of 1000 compared with 300 �mol quanta s-1 m-2 . Under some conditions NA continued at a reduced but steady rate in the presence of nitrate. NH4+ also markedly depressed NA but a concentration greater than 5 mM was needed to effect the same response. After NO3- was applied to an active symbiosis, nitrate reductase activity increased as NA decreased. Our results do not support the hypothesis of a direct effect of NO3- on nitrogenase due to the accumulation of toxic NO2-. Although our results allow that assimilate might be diverted from the nodules after the application of NO3- thus reducing N2-fixation, an alternative hypothesis is proposed: that nitrogenase and nitrate reductase work in a complementary manner in supplying reduced nitrogen to whole plants, and NO3- depresses N2-fixation through a regulatory system involving the level of soluble nitrogen in the plant. We conclude that nitrogen fixation by subterranean clover in the field may be depressed below its potential due to the presence of soil mineral nitrogen.

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Beaupied, Henri, André Moiroud, Anne-Marie Domenach, Fawaz Kurdali, and Robert Lensi. "Ratio of fixed and assimilated nitrogen in a black alder (Alnusglutinosa) stand." Canadian Journal of Forest Research 20, no. 7 (July 1, 1990): 1116–19. http://dx.doi.org/10.1139/x90-147.

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The ratio of fixed and assimilated nitrogen was determined in a black alder (Alnusglutinosa (L.) Gaertn.) stand throughout a growing season by measuring symbiotic dinitrogen fixation, soil mineral nitrogen concentration, and soil nitrifying capacity. The symbiotic dinitrogen fixation evaluated by the method based on natural isotopic abundance, δ15N) showed that most nitrogen present in alder leaves was derived from fixation (94%). Nitrogenase activity, measured by acetylene reduction assay, began at bud break and continued over the growing season, but showed great variation. The upper soil layer (0–15 cm) beneath black alder contained ammonium and nitrate nitrogen on sampling dates. Nitrification, determined by biological nitrous oxide (N2O) production after a short insitu incubation, occurred throughout the season. Black alders satisfied most of their nitrogen requirements from an atmospheric origin.

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Singh, B., and K. Usha. "Nodulation and symbiotic nitrogen fixation by genotypes of blackgram [Vigna mungo (L.) Hepper] as affected by fertiliser nitrogen." Australian Journal of Agricultural Research 53, no. 4 (2002): 453. http://dx.doi.org/10.1071/ar00156.

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Intercropping with legumes and non-legumes is commonly practised in many parts of the world to maximise productivity per unit area of land. In India, blackgram or urd [Vigna mungo (L.) Hepper] is a popular pulse legume component of intercropping farming systems. Often, however, potential production is compromised, particularly in high fertiliser input systems, because blackgram competes with the non-legume component of the system for nitrogen in the soil. In order to identify lines of blackgram that could obtain the majority of their nitrogen requirements from symbiotic fixation of atmospheric nitrogen rather than from uptake of soil nitrogen, 50 genotypes were screened for tolerance to (applied) nitrogen in soil. The parameters used to appraise tolerance were extent of root nodulation, the amount of nitrogen fixed, nitrate reductase activity in roots and nodules, and nitrite content of roots and nodules. There were 2 nitrogen treatments applied as urea, viz. 40 (N40) and 120 (N120) kg N per ha. There were 3 genotypes whose nitrogen-fixing effectiveness was apparently unimpaired by applications of nitrogen to the soil. Genotype NC-59308 nodulated and fixed atmospheric nitrogen satisfactorily at both the lower and higher levels of applied nitrogen. At N40, genotypes EC-48215 and PLU-726 formed a great abundance of large nodules effective in nitrogen fixation; even at N120, both lines had better symbioses than the majority of the 50 blackgram lines originally screened. These 3 genotypes are deemed worthy of further examination for their suitability for intercropping systems. How this might be done is discussed.

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Vicente, C. S. L., M. A. Pérez-Fernández, G. Pereira, and M. M. Tavares-de-Sousa. " Biological nitrogen fixation of Biserrula pelecinus L. under water deficit." Plant, Soil and Environment 58, No. 8 (August 21, 2012): 360–66. http://dx.doi.org/10.17221/786/2011-pse.

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The present work studied the effects of water deficiency conditions on the biological nitrogen fixation of three native rhizobia (SafPt12, SafPt6, and AjuPt16) isolated from Biserrula pelecinus L., and a reference strain Mesorhizobium ciceri biovar biserrulae. In terms of plant-water status, B. pelecinus showed typical signs of drought avoidance strategies such as reducing the aboveground development (i.e. reduction in leaf surface area and increase in root/shoot ratio) in detriment of a better developed root system. Dry-matter production and nitrogen content of the aboveground biomass decreased with the increasing levels of drought stress, as well as nodulation and symbiotic nitrogen fixation, for all the tested isolates. The parameters investigated suggested that SafPt12 was the most successful native rhizobia to withstand severe water conditions without compromising nitrogen fixation demands.    

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Lugomela, Charles, Brigitta Bergman, and John Waterbury. "Cyanobacterial diversity and nitrogen fixation in coastal areas around Zanzibar, Tanzania." Algological Studies/Archiv für Hydrobiologie, Supplement Volumes 103 (December 3, 2001): 95–115. http://dx.doi.org/10.1127/algol_stud/103/2001/95.

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Brewin, Nicholas J. "Legume root nodule symbiosis: An evolving story in biology and biotechnology." Biochemist 35, no. 4 (August 1, 2013): 14–18. http://dx.doi.org/10.1042/bio03504014.

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The evolution of biological nitrogen fixation is central to the evolution of life on earth. Nitrogen is an essential component of proteins and nucleic acids and its restricted availability to living organisms has often been a major factor limiting growth. Despite the overwhelming abundance of N2 gas in the atmosphere, di-nitrogen is chemically inaccessible to most forms of life. For their growth and metabolism, most organisms use the ‘fixed’ forms of nitrogen, either as ammonium (NH4+) or as nitrate (NO3-), or derivatives thereof. However, the major input into the global nitrogen cycle is through the reductive process of biological nitrogen fixation which converts atmospheric N2 into ammonia (NH3). This process evolved in bacteria and/or archaea over 2.5 billion years ago while the planet still had a reducing atmosphere. Today, biological nitrogen fixation is still restricted to the bacteria and archaea. The legume root nodule symbiosis allows the host plant to benefit directly by association with soil bacteria, collectively termed rhizobia, which fix nitrogen as endosymbionts.

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Zhang, Wenhui, Weiguo Hou, Xiangzhi Zeng, Shang Wang, and Hailiang Dong. "High Abundance of Thaumarchaeota Found in Deep Metamorphic Subsurface in Eastern China." Microorganisms 10, no. 3 (March 1, 2022): 542. http://dx.doi.org/10.3390/microorganisms10030542.

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Members of the Thaumarchaeota phylum play a key role in nitrogen cycling and are prevalent in a variety of environments including soil, sediment, and seawater. However, few studies have shown the presence of Thaumarchaeota in the terrestrial deep subsurface. Using high-throughput 16S rRNA gene sequencing, this study presents evidence for the high relative abundance of Thaumarchaeota in a biofilm sample collected from the well of Chinese Continental Scientific Drilling at a depth of 2000 m. Phylogenetic analysis showed a close relationship of these thaumarchaeotal sequences with known ammonia-oxidizing archaea (AOA) isolates, suggesting the presence of AOA in the deep metamorphic environment of eastern China which is believed to be oxic. Based on fluid geochemistry and FAProTax functional prediction, a pathway of nitrogen cycling is proposed. Firstly, heterotrophic nitrogen fixation is executed by diazotrophic bacteria coupled with methane oxidation. Then, ammonia is oxidized to nitrite by AOA, and nitrite is further oxidized to nitrate by bacteria within the phylum Nitrospirae. Denitrification and anaerobic ammonia oxidation occur slowly, leading to nitrate accumulation in the subsurface. With respect to biogeochemistry, the reaction between downward diffusing O2 and upward diffusing CH4 potentially fuels the ecosystem with a high relative abundance of Thaumarchaeota.

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35

Schwenke, G. D., M. B. Peoples, G. L. Turner, and D. F. Herridge. "Does nitrogen fixation of commercial, dryland chickpea and faba bean crops in north-west New South Wales maintain or enhance soil nitrogen?" Australian Journal of Experimental Agriculture 38, no. 1 (1998): 61. http://dx.doi.org/10.1071/ea97078.

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Summary. Nitrogen (N2 ) fixation accords pulse crops the potential to sustain or enhance total soil nitrogen (N) fertility. However, regional field experiments have shown that this potential is often not realised because N2 fixation is inhibited by the supply of nitrate N in the root zone (0–90 cm) coupled with a low demand for N during plant growth. The objectives of this study were to establish whether commercially grown chickpea and faba bean crops in the northern grain belt of New South Wales were depleting, maintaining or enhancing soil N fertility, and whether current farm management practices were maximising the N2 fixation potential of the crops. Fifty-one rainfed crops of chickpea (Cicer arietinum L.) and faba bean (Vicia faba L.) were surveyed in the Moree, Walgett and Gunnedah districts of north-west New South Wales during the winters of 1994 and 1995. Nitrogen fixation was measured using the natural 15N abundance technique. Net N balance was calculated for each crop by subtracting grain N harvested from fixed N2. Soil, plant and fallow conditions with potential to influence N2 fixation were also documented. The percentage of crop N derived from N2 fixation (Pfix) ranged from 0 to 81% for chickpea and 19 to 79% for faba bean. Nitrogen fixation of chickpea was uniformly low in the 1994 drought. Total N2 fixed ranged from 0 to 99 kg/ha for chickpea and 15 to 171 kg/ha for faba bean. Net N balance ranged from –47 to +46 kg N/ha for chickpea crops, and –12 to +94 kg N/ha for faba bean crops. About 60% of the difference in Pfix between chickpea and faba bean at the average level of soil nitrate (65 kg/ha) was explained by the higher N demand of the latter. The remaining 40% could be due to greater tolerance of the faba bean symbiosis to nitrate effects. In addition, faba bean had a lower N harvest index than chickpea, which meant that proportionally less N needed to be fixed by faba bean to offset removal of grain N. On average, Pfix needed to exceed 35% for chickpea and 19% for faba bean to balance soil N. The equivalent soil nitrate levels were 43 kg nitrate N/ha for chickpea and 280 kg/ha for faba bean (extrapolated from the relationship between measured Pfix and soil nitrate). Double-cropping chickpea into summer cereal or grass pasture stubble provided the most consistent strategy for achieving the low levels of soil nitrate.

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Hamilton, Trinity L., Evangeline Koonce, Alta Howells, Jeff R. Havig, Talia Jewell, José R. de la Torre, John W. Peters, and Eric S. Boyd. "Competition for Ammonia Influences the Structure of Chemotrophic Communities in Geothermal Springs." Applied and Environmental Microbiology 80, no. 2 (November 15, 2013): 653–61. http://dx.doi.org/10.1128/aem.02577-13.

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ABSTRACTSource waters sampled from Perpetual Spouter hot spring (pH 7.03, 86.4°C), Yellowstone National Park, WY, have low concentrations of total ammonia, nitrite, and nitrate, suggesting nitrogen (N) limitation and/or tight coupling of N cycling processes. Dominant small-subunit rRNA sequences in Perpetual Spouter source sediments are closely affiliated with the ammonia-oxidizing archaeon “CandidatusNitrosocaldus yellowstonii” and the putatively nitrogen-fixing (diazotrophic) bacteriumThermocrinis albus, respectively, suggesting that these populations may interact at the level of the bioavailable N pool, specifically, ammonia. This hypothesis was evaluated by using a combination of geochemical, physiological, and transcriptomic analyses of sediment microcosms. Amendment of microcosms with allylthiourea, an inhibitor of ammonia oxidation, decreased rates of acetylene reduction (a proxy for N2fixation) and nitrite production (a proxy for ammonia oxidation) and decreased transcript levels of structural genes involved in both nitrogen fixation (nifH) and ammonia oxidation (amoA). In contrast, amendment of microcosms with ammonia stimulated nitrite production and increasedamoAtranscript levels while it suppressed rates of acetylene reduction and decreasednifHtranscript levels. Sequencing of amplifiednifHandamoAtranscripts from native sediments, as well as microcosms, at 2 and 4 h postamendment, indicates that the dominant and responsive populations involved in ammonia oxidation and N2fixation are closely affiliated withCa. Nitrosocaldus yellowstonii andT. albus, respectively. Collectively, these results suggest that ammonia-oxidizing archaea, such asCa. Nitrosocaldus yellowstonii, have an apparent affinity for ammonia that is higher than that of the diazotrophs present in this ecosystem. Depletion of the bioavailable N pool through the activity of ammonia-oxidizing archaea likely represents a strong selective pressure for the inclusion of organisms capable of nitrogen fixation in geothermal communities. These observations help to explain the strong pattern in the codistribution of ammonia-oxidizing archaea and diazotrophs in circumneutral-to-alkaline geothermal springs.

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Somes, C. J., A. Oschlies, and A. Schmittner. "Isotopic constraints on the pre-industrial oceanic nitrogen budget." Biogeosciences Discussions 10, no. 2 (February 19, 2013): 3121–75. http://dx.doi.org/10.5194/bgd-10-3121-2013.

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Abstract. The size of the bio-available (i.e. "fixed") nitrogen inventory in the ocean influences global marine productivity and the biological carbon pump. Despite its importance, the pre-industrial rates for the major source and sink terms of the oceanic fixed nitrogen budget, N2 fixation and denitrification, respectively, are not well known. However, these processes leave distinguishable imprints on the ratio of stable nitrogen isotopes, δ15N, which can therefore help to infer their patterns and rates. Here we use δ15N observations from the water column and a new database of seafloor measurements to constrain rates of N2 fixation and denitrification predicted by a global three-dimensional Model of Ocean Biogeochemistry and Isotopes (MOBI). Sensitivity experiments were performed to quantify uncertainties associated with the isotope effect of denitrification in the water column and sediments. They show that the level of nitrate utilization in suboxic zones, that is the balance between nitrate consumption by denitrification and nitrate replenishment by mixing (dilution effect), significantly affects the isotope effect of water column denitrification and thus global mean δ15NO3−. Experiments with lower levels of nitrate utilization within the suboxic zone (i.e. higher residual water column nitrate concentrations, ranging from 20–32 μM) require higher ratios of benthic to water column denitrification (BD:WCD = 0.75–1.4, respectively), to satisfy the global mean NO3− and δ15NO3− constraints in the modern ocean. This suggests that nitrate utilization in suboxic zones play an important role in global nitrogen isotope cycling. Increasing the net fractionation factor for benthic denitrification (&varepsilon;BD = 0–4‰) requires even higher ratios of benthic to water column denitrification (BD:WCD = 1.4–3.5, respectively). The model experiments that best reproduce observed seafloor δ15N support the middle to high-end estimates for the net fractionation factor of benthic denitrification (&varepsilon;BD = 2–4‰). Assuming a balanced fixed nitrogen budget, we estimate that pre-industrial rates of N2 fixation, water column denitrification, and benthic denitrification were approximately 195–345, 65–75, and 130–270 Tg N yr−1, respectively. Although uncertainties still exist, these results suggest that previous estimates of N2 fixation have been significantly underestimated and the residence time for oceanic fixed nitrogen is between ~ 1500–3000 yr.

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Li, Zi-Yu, Li-Hui Mou, Gui-Duo Jiang, Qing-Yu Liu, and Sheng-Gui He. "¹⁵ N/¹⁴N isotopic exchange in the dissociative adsorption of N₂ on tantalum nitride cluster anions Ta₃N₃⁻." Chinese Journal of Chemical Physics 35, no. 1 (February 2022): 77–85. http://dx.doi.org/10.1063/1674-0068/cjcp2112286.

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Adsorption and activation of dinitrogen (N2) is an indispensable process in nitrogen fixation. Metal nitride species continue to attract attention as a promising catalyst for ammonia synthesis. However, the detailed mechanisms at a molecular level between reactive nitride species and N2 remain unclear at elevated temperature, which is important to understand the temperature effect and narrow the gap between the gas phase system and condensed phase system. Herein, the 14N/15N isotopic exchange in the reaction between tantalum nitride cluster anions Ta314N3− and 15N2 leading to the regeneration of 14N2/14N15N was observed at elevated temperature (393−593 K) using mass spectrometry. With the aid of theoretical calculations, the exchange mechanism and the effect of temperature to promote the dissociation of N2 on Ta3N3− were elucidated. A comparison experiment for Ta314N4−/15N2 couple indicated that only desorption of 15N2 from Ta314N415N2− took place at elevated temperature. The different exchange behavior can be well understood by the fact that nitrogen vacancy is a requisite for the dinitrogen activation over metal nitride species. This study may shed light on understanding the role of nitrogen vacancy in nitride species for ammonia synthesis and provide clues in designing effective catalysts for nitrogen fixation.

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39

O'GARA, FERGAL. "Nitrogen Fixation." Biochemical Society Transactions 13, no. 3 (June 1, 1985): 639. http://dx.doi.org/10.1042/bst0130639a.

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Wen-Yue Hsiung. "Nitrogen Fixation." Forest Ecology and Management 10, no. 4 (May 1985): 348–50. http://dx.doi.org/10.1016/0378-1127(85)90127-6.

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41

Becker, James Y., and Shlomit Avraham (Tsarfaty). "Nitrogen fixation." Journal of Electroanalytical Chemistry and Interfacial Electrochemistry 280, no. 1 (February 1990): 119–27. http://dx.doi.org/10.1016/0022-0728(90)87088-2.

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Becker, James Y., Shlomit Avraham (Tsarfaty), and Barry Posin. "Nitrogen fixation." Journal of Electroanalytical Chemistry and Interfacial Electrochemistry 230, no. 1-2 (August 1987): 143–53. http://dx.doi.org/10.1016/0022-0728(87)80138-9.

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43

Becker, James Y., and Barry Posin. "Nitrogen fixation." Journal of Electroanalytical Chemistry and Interfacial Electrochemistry 250, no. 2 (August 1988): 385–97. http://dx.doi.org/10.1016/0022-0728(88)85178-7.

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44

Shao, Shuai, Jun Zhang, Likun Li, Yuanhang Qin, Zhao-Qing Liu, and Tielin Wang. "Visible-light-driven photocatalytic N₂ fixation to nitrates by 2D/2D ultrathin BiVO₄ nanosheet/rGO nanocomposites." Chemical Communications 58, no. 13 (2022): 2184–87. http://dx.doi.org/10.1039/d1cc06750h.

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45

El Semary, Nermin Adel. "Adverse effects of nitrogenous compounds on nitrogen-fixing cyanobacterium Anabaena solitaria Klebahn." Bangladesh Journal of Botany 49, no. 4 (December 31, 2020): 1095–101. http://dx.doi.org/10.3329/bjb.v49i4.52558.

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The nitrogen-fixing heterocystous cyanobacterium Anabaena solitaria was tested for its response to different concentrations of nitrogen sources, namely nitrate and ammonia. To compare both the effect of concentration and type of nitrogen source, gradual concentrations were prepared for both ammonia and nitrate. The results showed concentration was significantly important on the frequency of heterocyst formation where highest nitrogen compounds concentrations were inhibitory for heterocyst formation. On the other hand, the effect of the type of nitrogenous compounds tested was insignificant which only proves that they are equally usable by cyanobacteria which will use them instead of transforming one of its cells to heterocyst thus not performing nitrogen fixation. Results also revealed the massive growth of heterotrophic bacteria in presence of nitrogenous compounds. This indicates that the presence of nitrogenous compounds in fields in which nitrogen-fixing cyanobacteria are to be used as biofertilizers can be inhibitory for nitrogen fixation and stimulatory for heterotrophic bacterial growth which could be pathogenic and harmful to plants. The use of more nitrogen-fixing cyanobacteria with the minimum amount of nitrogenous compounds is recommended.

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Zhang, Yao, Wei Qin, Lei Hou, Emily J. Zakem, Xianhui Wan, Zihao Zhao, Li Liu, et al. "Nitrifier adaptation to low energy flux controls inventory of reduced nitrogen in the dark ocean." Proceedings of the National Academy of Sciences 117, no. 9 (February 18, 2020): 4823–30. http://dx.doi.org/10.1073/pnas.1912367117.

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Ammonia oxidation to nitrite and its subsequent oxidation to nitrate provides energy to the two populations of nitrifying chemoautotrophs in the energy-starved dark ocean, driving a coupling between reduced inorganic nitrogen (N) pools and production of new organic carbon (C) in the dark ocean. However, the relationship between the flux of new C production and the fluxes of N of the two steps of oxidation remains unclear. Here, we show that, despite orders-of-magnitude difference in cell abundances between ammonia oxidizers and nitrite oxidizers, the two populations sustain similar bulk N-oxidation rates throughout the deep waters with similarly high affinities for ammonia and nitrite under increasing substrate limitation, thus maintaining overall homeostasis in the oceanic nitrification pathway. Our observations confirm the theoretical predictions of a redox-informed ecosystem model. Using balances from this model, we suggest that consistently low ammonia and nitrite concentrations are maintained when the two populations have similarly high substrate affinities and their loss rates are proportional to their maximum growth rates. The stoichiometric relations between the fluxes of C and N indicate a threefold to fourfold higher C-fixation efficiency per mole of N oxidized by ammonia oxidizers compared to nitrite oxidizers due to nearly identical apparent energetic requirements for C fixation of the two populations. We estimate that the rate of chemoautotrophic C fixation amounts to ∼1 × 1013to ∼2 × 1013mol of C per year globally through the flux of ∼1 × 1014to ∼2 × 1014mol of N per year of the two steps of oxidation throughout the dark ocean.

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Knapp, Angela N., Karen L. Casciotti, William M. Berelson, Maria G. Prokopenko, and Douglas G. Capone. "Low rates of nitrogen fixation in eastern tropical South Pacific surface waters." Proceedings of the National Academy of Sciences 113, no. 16 (March 14, 2016): 4398–403. http://dx.doi.org/10.1073/pnas.1515641113.

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An extensive region of the Eastern Tropical South Pacific (ETSP) Ocean has surface waters that are nitrate-poor yet phosphate-rich. It has been proposed that this distribution of surface nutrients provides a geochemical niche favorable for N2 fixation, the primary source of nitrogen to the ocean. Here, we present results from two cruises to the ETSP where rates of N2 fixation and its contribution to export production were determined with a suite of geochemical and biological measurements. N2 fixation was only detectable using nitrogen isotopic mass balances at two of six stations, and rates ranged from 0 to 23 µmol N m−2 d−1 based on sediment trap fluxes. Whereas the fractional importance of N2 fixation did not change, the N2-fixation rates at these two stations were several-fold higher when scaled to other productivity metrics. Regardless of the choice of productivity metric these N2-fixation rates are low compared with other oligotrophic locations, and the nitrogen isotope budgets indicate that N2 fixation supports no more than 20% of export production regionally. Although euphotic zone-integrated short-term N2-fixation rates were higher, up to 100 µmol N m−2 d−1, and detected N2 fixation at all six stations, studies of nitrogenase gene abundance and expression from the same cruises align with the geochemical data and together indicate that N2 fixation is a minor source of new nitrogen to surface waters of the ETSP. This finding is consistent with the hypothesis that, despite a relative abundance of phosphate, iron may limit N2 fixation in the ETSP.

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Mahmud, Kishan, Shiva Makaju, Razi Ibrahim, and Ali Missaoui. "Current Progress in Nitrogen Fixing Plants and Microbiome Research." Plants 9, no. 1 (January 13, 2020): 97. http://dx.doi.org/10.3390/plants9010097.

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In agroecosystems, nitrogen is one of the major nutrients limiting plant growth. To meet the increased nitrogen demand in agriculture, synthetic fertilizers have been used extensively in the latter part of the twentieth century, which have led to environmental challenges such as nitrate pollution. Biological nitrogen fixation (BNF) in plants is an essential mechanism for sustainable agricultural production and healthy ecosystem functioning. BNF by legumes and associative, endosymbiotic, and endophytic nitrogen fixation in non-legumes play major roles in reducing the use of synthetic nitrogen fertilizer in agriculture, increased plant nutrient content, and soil health reclamation. This review discusses the process of nitrogen-fixation in plants, nodule formation, the genes involved in plant-rhizobia interaction, and nitrogen-fixing legume and non-legume plants. This review also elaborates on current research efforts involved in transferring nitrogen-fixing mechanisms from legumes to non-legumes, especially to economically important crops such as rice, maize, and wheat at the molecular level and relevant other techniques involving the manipulation of soil microbiome for plant benefits in the non-legume root environment.

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Wang, Baomin, Leland S. Pierson, Christopher Rensing, Malkanthi K. Gunatilaka, and Christina Kennedy. "NasT-Mediated Antitermination Plays an Essential Role in the Regulation of the Assimilatory Nitrate Reductase Operon in Azotobacter vinelandii." Applied and Environmental Microbiology 78, no. 18 (July 6, 2012): 6558–67. http://dx.doi.org/10.1128/aem.01720-12.

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ABSTRACTAzotobacter vinelandiiis a well-studied model system for nitrogen fixation in bacteria. Regulation of nitrogen fixation inA. vinelandiiis independent of NtrB/NtrC, a conserved nitrogen regulatory system in proteobacteria. Previous work showed that anntrCmutation inA. vinelandiiresulted in a loss of induction of assimilatory nitrate and nitrite reductases encoded by thenasABoperon. In addition to NtrC, several other proteins, including NasT, a protein containing a potential RNA-binding domain ANTAR (AmiR andNasRtranscriptionantiterminationregulators), have been implicated innasABregulation. In this work, we characterize the sequence upstream ofnasAand identify several DNA sequence elements, including two potential NtrC binding sites and a putative intrinsic transcriptional terminator upstream ofnasAthat are potentially involved innasABregulation. Our analyses confirm that thenasABpromoter,PnasA, is under NtrC control. However, unlike NtrC-regulated promoters in enteric bacteria,PnasAshows high activity in the presence of ammonium; in addition, thePnasAactivity is altered in thenifAgene mutation background. We discuss the implication of these results on NtrC-mediated regulation inA. vinelandii. Our study provides direct evidence that induction ofnasABis regulated by NasT-mediated antitermination, which occurs within the leader region of the operon. The results also support the hypothesis that NasT binds the promoter proximal hairpin ofnasABfor its regulatory function, which contributes to the understanding of the regulatory mechanism of ANTAR-containing antiterminators.

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Rolff, C., R. Elmgren, and M. Voss. "Deposition of nitrogen and phosphorus on the Baltic Sea: seasonal patterns and nitrogen isotope composition." Biogeosciences Discussions 5, no. 4 (August 6, 2008): 3013–44. http://dx.doi.org/10.5194/bgd-5-3013-2008.

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Abstract. Atmospheric deposition of nitrogen and phosphorus on the Baltic Proper was estimated monthly at two coastal stations and two isolated islands in 2001 and 2002. Yearly nitrogen deposition ranged between 387 and 727 mg N m−2 yr−1 (average ~617) and was composed of ~10% organic N and approximately equal amounts of ammonium and nitrate. Winter nitrate peaks at the isolated islands possibly indicated ship emissions. Load weighted δ15N of deposited N was 3.7‰ and 0.35‰ at the coastal stations and the isolated islands respectively. Winter δ15N was ~3‰ lighter than in summer, reflecting winter dominance of nitrate. The light isotopic composition of deposited nitrogen may cause overestimates of nitrogen fixation in basin-wide isotopic budgeting, whereas relatively heavy deposition of ammonium during summer instead may cause underestimates of fixation in budgets of the upper mixed layer. δ15N in atmospherically deposited nitrate and ammonium was estimated by regression to –7.9 and 13.5‰ respectively. Phosphorus deposition showed no clear seasonal pattern and was considerably lower at the isolated islands. Organic P constituted 20–40% of annual P deposition. P deposition is unlikely to be a major source for cyanobacterial blooms but may potentially prolong an ongoing bloom.

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Journal articles on the topic 'Nitroge fixation'

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