Articoli di riviste: "Nitrogen fixation and transfer"

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George, T. Adrian, e Bharat B. Kaul. "Electron transfer in inorganic nitrogen fixation". Inorganic Chemistry 30, n. 5 (marzo 1991): 882–83. http://dx.doi.org/10.1021/ic00005a004.

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Farnham, D. E., e J. R. George. "Dinitrogen fixation and nitrogen transfer among red clover cultivars". Canadian Journal of Plant Science 73, n. 4 (1 ottobre 1993): 1047–54. http://dx.doi.org/10.4141/cjps93-136.

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Red clover (Trifolium pratense L.) is an important perennial forage legume used for hay or as pasture in crop rotations. Despite its traditional usage as a source of nitrogen (N) for cropping systems, little information is available on the amounts of atmospheric dinitrogen (N2) that red clover fixes or transfers to an associated grass during long-term stands. Field research was undertaken in 1989 and 1990 to compare N2 fixation and N transfer potentials of one experimental and three common red clover cultivars seeded in binary mixtures with orchardgrass (Dactylis glomerata L.). Dinitrogen fixation and N transfer were estimated by 15N isotope dilution using orchardgrass pure stands as a reference. Over the 2-yr study, percentage legume N derived from N2 fixation ranged from 96.4 to 96.7% among the red clover cultivars. Total-season fixed-N yields in red clover herbage ranged from 72.6 to 159.2 kg ha−1. Dinitrogen fixation and fixed-N yields usually did not differ among red clover cultivars in either year. Percentage N in orchardgrass herbage derived from N2 fixation by red clover ranged from 43.7 to 70.5%. Total-season transferred-N yields in orchardgrass herbage was 16.9 kg ha−1 in 1989 and 57.8 kg ha−1 in 1990. Neither N-transfer nor transferred-N yield differed among cultivars in either year. It is concluded that, under the conditions of this study, the red clover cultivars tested generally did not differ in their abilities to fix atmospheric N2 or to transfer fixed-N to associated orchardgrass. Key words: Red clover, Trifolium pratense L., dinitrogen fixation, nitrogen transfer, isotope dilution

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Stern, W. R. "Nitrogen fixation and transfer in intercrop systems". Field Crops Research 34, n. 3-4 (settembre 1993): 335–56. http://dx.doi.org/10.1016/0378-4290(93)90121-3.

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Katz, Faith E. H., Cedric P. Owens e F. A. Tezcan. "Electron Transfer Reactions in Biological Nitrogen Fixation". Israel Journal of Chemistry 56, n. 9-10 (18 luglio 2016): 682–92. http://dx.doi.org/10.1002/ijch.201600020.

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Rees, Douglas C., F. Akif Tezcan, Chad A. Haynes, Mika Y. Walton, Susana Andrade, Oliver Einsle e James B. Howard. "Structural basis of biological nitrogen fixation". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 363, n. 1829 (5 aprile 2005): 971–84. http://dx.doi.org/10.1098/rsta.2004.1539.

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Biological nitrogen fixation is mediated by the nitrogenase enzyme system that catalyses the ATP dependent reduction of atmospheric dinitrogen to ammonia. Nitrogenase consists of two component metalloproteins, the MoFe-protein with the FeMo-cofactor that provides the active site for substrate reduction, and the Fe-protein that couples ATP hydrolysis to electron transfer. An overview of the nitrogenase system is presented that emphasizes the structural organization of the proteins and associated metalloclusters that have the remarkable ability to catalyse nitrogen fixation under ambient conditions. Although the mechanism of ammonia formation by nitrogenase remains enigmatic, mechanistic inferences motivated by recent developments in the areas of nitrogenase biochemistry, spectroscopy, model chemistry and computational studies are discussed within this structural framework.

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Jiao, Jian, Li Juan Wu, Biliang Zhang, Yue Hu, Yan Li, Xing Xing Zhang, Hui Juan Guo et al. "MucR Is Required for Transcriptional Activation of Conserved Ion Transporters to Support Nitrogen Fixation of Sinorhizobium fredii in Soybean Nodules". Molecular Plant-Microbe Interactions® 29, n. 5 (maggio 2016): 352–61. http://dx.doi.org/10.1094/mpmi-01-16-0019-r.

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To achieve effective symbiosis with legume, rhizobia should fine-tune their background regulation network in addition to activating key genes involved in nodulation (nod) and nitrogen fixation (nif). Here, we report that an ancestral zinc finger regulator, MucR1, other than its paralog, MucR2, carrying a frameshift mutation, is essential for supporting nitrogen fixation of Sinorhizobium fredii CCBAU45436 within soybean nodules. In contrast to the chromosomal mucR1, mucR2 is located on symbiosis plasmid, indicating its horizontal transfer potential. A MucR2 homolog lacking the frameshift mutation, such as the one from S. fredii NGR234, can complement phenotypic defects of the mucR1 mutant of CCBAU45436. RNA-seq analysis revealed that the MucR1 regulon of CCBAU45436 within nodules exhibits significant difference compared with that of free-living cells. MucR1 is required for active expression of transporters for phosphate, zinc, and elements essential for nitrogenase activity (iron, molybdenum, and sulfur) in nodules but is dispensable for transcription of key genes (nif/fix) involved in nitrogen fixation. Further reverse genetics suggests that S. fredii uses high-affinity transporters to meet the demand for zinc and phosphate within nodules. These findings, together with the horizontal transfer potential of the mucR homolog, imply an intriguing evolutionary role of this ancestral regulator in supporting nitrogen fixation.

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Inomura, Keisuke, Christopher L. Follett, Takako Masuda, Meri Eichner, Ondřej Prášil e Curtis Deutsch. "Carbon Transfer from the Host Diatom Enables Fast Growth and High Rate of N2 Fixation by Symbiotic Heterocystous Cyanobacteria". Plants 9, n. 2 (4 febbraio 2020): 192. http://dx.doi.org/10.3390/plants9020192.

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Diatom–diazotroph associations (DDAs) are symbioses where trichome-forming cyanobacteria support the host diatom with fixed nitrogen through dinitrogen (N2) fixation. It is inferred that the growth of the trichomes is also supported by the host, but the support mechanism has not been fully quantified. Here, we develop a coarse-grained, cellular model of the symbiosis between Hemiaulus and Richelia (one of the major DDAs), which shows that carbon (C) transfer from the diatom enables a faster growth and N2 fixation rate by the trichomes. The model predicts that the rate of N2 fixation is 5.5 times that of the hypothetical case without nitrogen (N) transfer to the host diatom. The model estimates that 25% of fixed C from the host diatom is transferred to the symbiotic trichomes to support the high rate of N2 fixation. In turn, 82% of N fixed by the trichomes ends up in the host. Modeled C fixation from the vegetative cells in the trichomes supports only one-third of their total C needs. Even if we ignore the C cost for N2 fixation and for N transfer to the host, the total C cost of the trichomes is higher than the C supply by their own photosynthesis. Having more trichomes in a single host diatom decreases the demand for N2 fixation per trichome and thus decreases their cost of C. However, even with five trichomes, which is about the highest observed for Hemiaulus and Richelia symbiosis, the model still predicts a significant C transfer from the diatom host. These results help quantitatively explain the observed high rates of growth and N2 fixation in symbiotic trichomes relative to other aquatic diazotrophs.

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Foster, Rachel A., Marcel M. M. Kuypers, Tomas Vagner, Ryan W. Paerl, Niculina Musat e Jonathan P. Zehr. "Nitrogen fixation and transfer in open ocean diatom–cyanobacterial symbioses". ISME Journal 5, n. 9 (31 marzo 2011): 1484–93. http://dx.doi.org/10.1038/ismej.2011.26.

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McNeill, A. M., e M. Wood. "Fixation and transfer of nitrogen by white clover to ryegrass". Soil Use and Management 6, n. 2 (giugno 1990): 84–86. http://dx.doi.org/10.1111/j.1475-2743.1990.tb00810.x.

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Farnham, Dale E., e J. Ronald George. "Dinitrogen Fixation and Nitrogen Transfer in Birdsfoot Trefoil–Orchardgrass Communities". Agronomy Journal 86, n. 4 (luglio 1994): 690–94. http://dx.doi.org/10.2134/agronj1994.00021962008600040019x.

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Li, Qin, e Sanfeng Chen. "Transfer of Nitrogen Fixation ( nif ) Genes to Non‐diazotrophic Hosts". ChemBioChem 21, n. 12 (2 marzo 2020): 1717–22. http://dx.doi.org/10.1002/cbic.201900784.

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Papastylianou, I., e S. K. A. Danso. "Nitrogen fixation and transfer in vetch and vetch-oats mixtures". Soil Biology and Biochemistry 23, n. 5 (gennaio 1991): 447–52. http://dx.doi.org/10.1016/0038-0717(91)90008-8.

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Hatzell, Marta, e Yu-Hsuan Liu. "A Spectroscopic Investigation of Photochemical Nitrogen Fixation". ECS Meeting Abstracts MA2022-01, n. 40 (7 luglio 2022): 1810. http://dx.doi.org/10.1149/ma2022-01401810mtgabs.

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Photochemical nitrogen transformations were initially pioneered by a prominent Indian soil scientist, N.R. Dhar, in the 1930-40s[1]. Others continued to evaluate this process in the presence of liquid water, water vapor, and oxygen. These results remained unverified until 1977, when Schrauzer and Guth also began to investigate this process on natural minerals[2]. Since the 1970s photochemical nitrogen fixation has been widely studied on a number of photocatalyst[3]. Most conclude that nitrogen is reduce to ammonia through a direct electron-transfer based process. However, the reaction mechanism has not been clearly mapped using spectroscopic techniques. Here, we examine the reaction pathway for nitrogen fixation to ammonia on titania based photocatalyst using multiple spectroscopic techniques. We also aim to focus our talk on explaining the role hole scavengers play in enabling this reaction. [1]Dhar, N. R., and N. N. Pant. "Nitrogen loss from soils and oxide surfaces." Nature 153.3873 (1944): 115-116. [2] GN Schrauzer and TD Guth. Photocatalytic reactions. 1. Photolysis of water and photoreduction of nitrogen on titanium dioxide. Journal of the American Chemical Society, 99(22):7189–7193,1977. [3]Medford, Andrew J., and Marta C. Hatzell. "Photon-driven nitrogen fixation: current progress, thermodynamic considerations, and future outlook." Acs Catalysis 7.4 (2017): 2624-2643.

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Zhang, Zhengcheng, Yoko Masuda, Zhenxing Xu, Yutaka Shiratori, Hirotomo Ohba e Keishi Senoo. "Active Nitrogen Fixation by Iron-Reducing Bacteria in Rice Paddy Soil and Its Further Enhancement by Iron Application". Applied Sciences 13, n. 14 (13 luglio 2023): 8156. http://dx.doi.org/10.3390/app13148156.

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In rice paddy soil, biological nitrogen fixation is important for sustaining soil nitrogen fertility and rice growth. Anaeromyxobacter and Geobacteriaceae, iron-reducing bacteria belonging to Deltaproteobacteria, are newly discovered nitrogen-fixing bacteria dominant in paddy soils. They utilize acetate, a straw-derived major carbon compound in paddy soil, as a carbon and energy source, and ferric iron compounds as electron acceptors for anaerobic respiration. In our previous paddy field experiments, a significant increase in soil nitrogen-fixing activity was observed after the application of iron powder to straw-returned paddy field soil. In addition, combining iron application with 60–80% of the conventional nitrogen fertilizer rate could maintain rice yields similar to those with the conventional nitrogen fertilization rate. It was thus suggested that iron application to paddy soil increased the amount of nitrogen fixed in the soil by enhancing nitrogen fixation by diazotrophic iron-reducing bacteria. The present study was conducted to directly verify this suggestion by 15N-IRMS analysis combined with 15N-DNA-stable isotope probing of iron-applied and no-iron-applied plot soils in an experimental paddy field. In no-iron-applied native paddy soil, atmospheric 15N2 was incorporated into the soil by biological nitrogen fixation, in which diazotrophic iron-reducing bacteria were the most active drivers of nitrogen fixation. In iron-applied paddy soil, the amount of 15N incorporated into the soil was significantly higher due to enhanced biological nitrogen fixation, especially via diazotrophic iron-reducing bacteria, the most active drivers of nitrogen fixation in the soil. Thus, our previous suggestion was verified. This study provided a novel picture of active nitrogen-fixing microorganisms dominated by diazotrophic iron-reducing bacteria in paddy soil, and directly proved the effectiveness of iron application to enhance their nitrogen fixation and increase the incorporation of atmospheric nitrogen into soil. The enhancement of biological nitrogen fixation in paddy fields by iron application may lead to novel and unique paddy soil management strategies to increase soil nitrogen fertility and ensure rice yields with reduced nitrogen fertilizer input and lower environmental nitrogen burdens.

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Yang, Ling-Ling, Zhao Jiang, Yan Li, En-Tao Wang e Xiao-Yang Zhi. "Plasmids Related to the Symbiotic Nitrogen Fixation Are Not Only Cooperated Functionally but Also May Have Evolved over a Time Span in Family Rhizobiaceae". Genome Biology and Evolution 12, n. 11 (20 luglio 2020): 2002–14. http://dx.doi.org/10.1093/gbe/evaa152.

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Abstract Rhizobia are soil bacteria capable of forming symbiotic nitrogen-fixing nodules associated with leguminous plants. In fast-growing legume-nodulating rhizobia, such as the species in the family Rhizobiaceae, the symbiotic plasmid is the main genetic basis for nitrogen-fixing symbiosis, and is susceptible to horizontal gene transfer. To further understand the symbioses evolution in Rhizobiaceae, we analyzed the pan-genome of this family based on 92 genomes of type/reference strains and reconstructed its phylogeny using a phylogenomics approach. Intriguingly, although the genetic expansion that occurred in chromosomal regions was the main reason for the high proportion of low-frequency flexible gene families in the pan-genome, gene gain events associated with accessory plasmids introduced more genes into the genomes of nitrogen-fixing species. For symbiotic plasmids, although horizontal gene transfer frequently occurred, transfer may be impeded by, such as, the host’s physical isolation and soil conditions, even among phylogenetically close species. During coevolution with leguminous hosts, the plasmid system, including accessory and symbiotic plasmids, may have evolved over a time span, and provided rhizobial species with the ability to adapt to various environmental conditions and helped them achieve nitrogen fixation. These findings provide new insights into the phylogeny of Rhizobiaceae and advance our understanding of the evolution of symbiotic nitrogen fixation.

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Soumare, Abdoulaye, Abdala G. Diedhiou, Moses Thuita, Mohamed Hafidi, Yedir Ouhdouch, Subramaniam Gopalakrishnan e Lamfeddal Kouisni. "Exploiting Biological Nitrogen Fixation: A Route Towards a Sustainable Agriculture". Plants 9, n. 8 (11 agosto 2020): 1011. http://dx.doi.org/10.3390/plants9081011.

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For all living organisms, nitrogen is an essential element, while being the most limiting in ecosystems and for crop production. Despite the significant contribution of synthetic fertilizers, nitrogen requirements for food production increase from year to year, while the overuse of agrochemicals compromise soil health and agricultural sustainability. One alternative to overcome this problem is biological nitrogen fixation (BNF). Indeed, more than 60% of the fixed N on Earth results from BNF. Therefore, optimizing BNF in agriculture is more and more urgent to help meet the demand of the food production needs for the growing world population. This optimization will require a good knowledge of the diversity of nitrogen-fixing microorganisms, the mechanisms of fixation, and the selection and formulation of efficient N-fixing microorganisms as biofertilizers. Good understanding of BNF process may allow the transfer of this ability to other non-fixing microorganisms or to non-leguminous plants with high added value. This minireview covers a brief history on BNF, cycle and mechanisms of nitrogen fixation, biofertilizers market value, and use of biofertilizers in agriculture. The minireview focuses particularly on some of the most effective microbial products marketed to date, their efficiency, and success-limiting in agriculture. It also highlights opportunities and difficulties of transferring nitrogen fixation capacity in cereals.

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Bothe, Hermann, Oliver Schmitz, M. Geoffrey Yates e William E. Newton. "Nitrogen Fixation and Hydrogen Metabolism in Cyanobacteria". Microbiology and Molecular Biology Reviews 74, n. 4 (dicembre 2010): 529–51. http://dx.doi.org/10.1128/mmbr.00033-10.

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SUMMARY This review summarizes recent aspects of (di)nitrogen fixation and (di)hydrogen metabolism, with emphasis on cyanobacteria. These organisms possess several types of the enzyme complexes catalyzing N2 fixation and/or H2 formation or oxidation, namely, two Mo nitrogenases, a V nitrogenase, and two hydrogenases. The two cyanobacterial Ni hydrogenases are differentiated as either uptake or bidirectional hydrogenases. The different forms of both the nitrogenases and hydrogenases are encoded by different sets of genes, and their organization on the chromosome can vary from one cyanobacterium to another. Factors regulating the expression of these genes are emerging from recent studies. New ideas on the potential physiological and ecological roles of nitrogenases and hydrogenases are presented. There is a renewed interest in exploiting cyanobacteria in solar energy conversion programs to generate H2 as a source of combustible energy. To enhance the rates of H2 production, the emphasis perhaps needs not to be on more efficient hydrogenases and nitrogenases or on the transfer of foreign enzymes into cyanobacteria. A likely better strategy is to exploit the use of radiant solar energy by the photosynthetic electron transport system to enhance the rates of H2 formation and so improve the chances of utilizing cyanobacteria as a source for the generation of clean energy.

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Tao, Ran, Xinghua Li, Xiaowei Li, Changlu Shao e Yichun Liu. "TiO2/SrTiO3/g-C3N4 ternary heterojunction nanofibers: gradient energy band, cascade charge transfer, enhanced photocatalytic hydrogen evolution, and nitrogen fixation". Nanoscale 12, n. 15 (2020): 8320–29. http://dx.doi.org/10.1039/d0nr00219d.

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Dong, Fangyuan, Yoo Seok Lee, Erin M. Gaffney, Willisa Liou e Shelley D. Minteer. "Engineering Cyanobacterium with Transmembrane Electron Transfer Ability for Bioelectrochemical Nitrogen Fixation". ACS Catalysis 11, n. 21 (15 ottobre 2021): 13169–79. http://dx.doi.org/10.1021/acscatal.1c03038.

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Heichel, G. H., e K. I. Henjum. "Dinitrogen Fixation, Nitrogen Transfer, and Productivity of Forage Legume‐Grass Communities". Crop Science 31, n. 1 (gennaio 1991): 202–8. http://dx.doi.org/10.2135/cropsci1991.0011183x003100010045x.

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Rao, A. V., e Kenneth E. Giller. "Nitrogen fixation and its transfer from Leucaena to grass using 15N". Forest Ecology and Management 61, n. 3-4 (novembre 1993): 221–27. http://dx.doi.org/10.1016/0378-1127(93)90203-y.

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Mulholland, M. R. "The fate of nitrogen fixed by diazotrophs in the ocean". Biogeosciences 4, n. 1 (12 gennaio 2007): 37–51. http://dx.doi.org/10.5194/bg-4-37-2007.

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Abstract. While we now know that N2 fixation is a significant source of new nitrogen (N) in the marine environment, little is known about the fate of this N (and associated C), despite the importance of diazotrophs to global carbon and nutrient cycles. Specifically, does N fixed during N2 fixation fuel autotrophic or heterotrophic growth and thus facilitate carbon (C) export from the euphotic zone, or does it contribute primarily to bacterial productivity and respiration in the euphotic zone? For Trichodesmium, the diazotroph we know the most about, the transfer of recently fixed N2 (and C) appears to be primarily through dissolved pools. The release of N varies among and within populations and as a result of the changing physiological state of cells and populations. The net result of trophic transfers appears to depend on the co-occurring organisms and the complexity of the colonizing community. In order to understand the impact of diazotrophy on carbon flow and export in marine systems, we need a better understanding of the trophic flow of elements in Trichodesmium-dominated communities and other diazotrophic communities under various defined physiological states. Nitrogen and carbon fixation rates themselves vary by orders of magnitude within and among studies of Trichodesmium, highlighting the difficulty in extrapolating global rates of N2 fixation from direct measurements. Because the stoichiometry of N2 and C fixation does not appear to be in balance with that of particles, and the relationship between C and N2 fixation rates is also variable, it is equally difficult to derive global rates of one from the other. This paper seeks to synthesize what is known about the fate of diazotrophic production in the environment. A better understanding of the physiology and physiological ecology of Trichodesmium and other marine diazotrophs is necessary to quantify and predict the effects of increased or decreased diazotrophy in the context of the carbon cycle and global change.

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Gerard, V. A., S. E. Dunham e G. Rosenberg. "Nitrogen-fixation by cyanobacteria associated withCodium fragile (Chlorophyta): Environmental effects and transfer of fixed nitrogen". Marine Biology 105, n. 1 (febbraio 1990): 1–8. http://dx.doi.org/10.1007/bf01344264.

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Chen, Hao, Yuye Jiang, Kai Zhu, Jingwen Yang, Yanxia Fu e Shuang Wang. "A Review on Industrial CO2 Capture through Microalgae Regulated by Phytohormones and Cultivation Processes". Energies 16, n. 2 (12 gennaio 2023): 897. http://dx.doi.org/10.3390/en16020897.

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Microalgae is a promising metabolism microorganism for the fixation of CO2 from industrial gas while accumulating microalgae biomass. The process of CO2 fixation by microalgae is able to be significantly improved by the regulation of phytohormones. However, the complex metabolic mechanism of microalgae regulated by phytohormones and abiotic stress on CO2 fixation deserves to be explored. To systematically understand the existing status and establish a foundation for promoting the technology, this paper reviews investigations on the metabolic mechanism of microalgae regulated by phytohormones. The influences of nitrogen stress, light intensity stress, heavy metal stress, and salinity stress on CO2 fixation and lipid production are summarized. In addition, a comprehensive overview of the multistage regulation of phytohormones and abiotic stress on CO2 fixation and lipid production through microalgae is presented. The recent advances in CO2 transfer reinforcement and light transmission reinforcement in photobioreactors are discussed. This review provides an insight into the enhancement of CO2 fixation by microalgae regulated by phytohormones, abiotic stress, and mass transfer in multistage photobioreactors.

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Dantas, Edilândia Farias, Ana Dolores Santiago de Freitas, Maria do Carmo Catanho Pereira de Lyra, Carolina Etienne de Rosália e. Silva Santos, Stella Jorge de Carvalho Neta, Augusto Cesar de Arruda Santana, Rosemberg de Vasconcelos Bezerra e Everardo Valadares de Sá Barretto Sampaio. "Biological fixation, transfer and balance of nitrogen in passion fruit (Passiflora edulis Sims) orchard intercropped with different green manure crops". 2019 13, (03) 2019 (20 marzo 2019): 465–71. http://dx.doi.org/10.21475/ajcs.19.13.03.p1559.

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Green manures can replace or supplement mineral fertilization and add organic matter to the soils, ensuring greater sustainability to fruit growing in semiarid regions. Biological fixation, transfer and balance of nitrogen were determined on an irrigated yellow passion fruit orchard (Passiflora edulis Sims) intercropped separately with three cover crops: sunn hemp, Crotalaria juncea (L.); pigeon pea, Cajanus cajan (L.) Mill; and jack bean, Canavalia ensiformis (L.) DC. In a fourth treatment, legumes were not planted, but spontaneous vegetation was left to grow freely. The legumes were croped for 90 days in three lines (0.5 m apart) inside the passion fruit plant lines (2.5 m apart). Fixation and transfers were determined by the 15N natural abundance technique, using sunflower as a reference plant. The three planted legumes nodulated abundantly and fixed nitrogen in high proportions (between 50 and 90% of their N), forming symbiosis with bacteria naturally established in the soil. Jack bean produced more biomass than sunn hemp and pigeon pea, and as much as the spontaneous plants, of which 23% were legumes. The amounts of fixed N (150, 43, 30 and 29 kg ha-1) were determined mainly by the biomass of legumes. More than 40% of the N of passion fruit plants came from the biological nitrogen fixation of the intercropped jack bean, which provided an amount of N higher than that exported in the fruits, generating a positive balance of more than 100 kg ha-1. Therefore, it is recommended to intercrop jack bean in irrigated passion fruit orchards.

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Wood, Craig C., Nazrul Islam, Raymond J. Ritchie e Ivan R. Kennedy. "A simplified model for assessing critical parameters during associative 15N2 fixation between Azospirillum and wheat". Functional Plant Biology 28, n. 9 (2001): 969. http://dx.doi.org/10.1071/pp01036.

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This paper originates from an address at the 8th International Symposium on Nitrogen Fixation with Non-Legumes, Sydney, NSW, December 2000 Detailed studies in field experiments have shown repeatedly that the transfer of 15N2 fixed by diazotrophic bacteria to wheat tissue is minimal. Here, a simple and convenient laboratory co-culture model was designed to assess important features of the association between Azospirillum brasilense and wheat, such as the rate of nitrogen fixation (acetylene reduction), ammonia excretion from the bacterium and the transfer of newly fixed 15N2 from the associative diazotroph to the shoot tissue of wheat plants. After 70 h, in this model, insignificant amounts of newly fixed N2 were transferred from an ammonia-excreting strain of A. brasilense to the shoot tissue of wheat. However, when malate was added to the co-culture the 15N enrichment of the shoot tissue increased 48-fold, indicating that 20% of shoot N had been derived from N2 fixation. Thus, the inability of the host plant to release carbon in the rhizosphere is a significant constraint in the development of associative N2-fixing systems. These specific results suggest that wheat plants with an increased release of photosynthate to the rhizosphere should be a priority for the future development of broad-acre agricultural systems that are more self-sufficient for nitrogen nutrition. The simplicity of the model for assessing the critical parameters of associative 15N2 fixation may allow large-scale surveys of plant–bacterial interactions to be conducted and a selection of improved associations for further study.

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Yuan, Menglei, Yiling Bai, Jingxian Zhang, Tongkun Zhao, Shuwei Li, Hongyan He, Zhanjun Liu, Zhongde Wang e Guangjin Zhang. "Work function regulation of nitrogen-doped carbon nanotubes triggered by metal nanoparticles for efficient electrocatalytic nitrogen fixation". Journal of Materials Chemistry A 8, n. 48 (2020): 26066–74. http://dx.doi.org/10.1039/d0ta08914a.

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The work function (W) is utilized as an effective descriptor to predict the electrochemical nitrogen reduction reaction (NRR) activity. The lower W value of M@NCNTs promotes the transfer of electrons from the catalyst surface to the adsorbed N₂.

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Cantera, Jose Jason L., Hiroko Kawasaki e Tatsuji Seki. "The nitrogen-fixing gene (nifH) of Rhodopseudomonas palustris: a case of lateral gene transfer?" Microbiology 150, n. 7 (1 luglio 2004): 2237–46. http://dx.doi.org/10.1099/mic.0.26940-0.

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Nitrogen fixation is catalysed by some photosynthetic bacteria. This paper presents a phylogenetic comparison of a nitrogen fixation gene (nifH) with the aim of elucidating the processes underlying the evolutionary history of Rhodopseudomonas palustris. In the NifH phylogeny, strains of Rps. palustris were placed in close association with Rhodobacter spp. and other phototrophic purple non-sulfur bacteria belonging to the α-Proteobacteria, separated from its close relatives Bradyrhizobium japonicum and the phototrophic rhizobia (Bradyrhizobium spp. IRBG 2, IRBG 228, IRBG 230 and BTAi 1) as deduced from the 16S rRNA phylogeny. The close association of the strains of Rps. palustris with those of Rhodobacter and Rhodovulum, as well as Rhodospirillum rubrum, was supported by the mol% G+C of their nifH gene and by the signature sequences found in the sequence alignment. In contrast, comparison of a number of informational and operational genes common to Rps. palustris CGA009, B. japonicum USDA 110 and Rhodobacter sphaeroides 2.4.1 suggested that the genome of Rps. palustris is more related to that of B. japonicum than to the Rba. sphaeroides genome. These results strongly suggest that the nifH of Rps. palustris is highly related to those of the phototrophic purple non-sulfur bacteria included in this study, and might have come from an ancestral gene common to these phototrophic species through lateral gene transfer. Although this finding complicates the use of nifH to infer the phylogenetic relationships among the phototrophic bacteria in molecular diversity studies, it establishes a framework to resolve the origins and diversification of nitrogen fixation among the phototrophic bacteria in the α-Proteobacteria.

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Carlsson, Georg, e Kerstin Huss-Danell. "Does nitrogen transfer between plants confound 15N-based quantifications of N2 fixation?" Plant and Soil 374, n. 1-2 (5 settembre 2013): 345–58. http://dx.doi.org/10.1007/s11104-013-1802-1.

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Haby, Vincent A., Stephen A. Stout, Frank M. Hons e Allen T. Leonard. "Nitrogen Fixation and Transfer in a Mixed Stand of Alfalfa and Bermudagrass". Agronomy Journal 98, n. 4 (luglio 2006): 890–98. http://dx.doi.org/10.2134/agronj2005.0084.

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31

Chen, Shanshan, Xintong Han, Shuyi Xie, Yuting Yang, Xianyue Jing e Tiangang Luan. "Extracellular electron transfer drives ATP synthesis for nitrogen fixation by Pseudomonas stutzeri". Electrochemistry Communications 154 (settembre 2023): 107562. http://dx.doi.org/10.1016/j.elecom.2023.107562.

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32

Liu, Nianhua, Rong Tang, Kai Li, Bin Wang, Junze Zhao, Qing Xu, Mengxia Ji e Jiexiang Xia. "Steering Charge Directional Separation in MXenes/Titanium Dioxide for Efficient Photocatalytic Nitrogen Fixation". Catalysts 13, n. 12 (30 novembre 2023): 1487. http://dx.doi.org/10.3390/catal13121487.

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Abstract (sommario):

Photocatalytic nitrogen fixation has attracted much attention because of its ability to synthesize ammonia under mild conditions. However, the ammonia yield is still greatly limited by the sluggish charge separation and extremely high N2 dissociation energy. Herein, two-dimensional Ti3C2 MXene ultrathin nanosheets were introduced to construct Ti3C2/TiO2 composites via electrostatic adsorption for photocatalytic nitrogen fixation. The photocatalytic activity experiments showed that after adding 0.1 wt% Ti3C2, the ammonia yield of the Ti3C2/TiO2 composite reached 67.9 μmol L−1 after 120 min of light irradiation, nearly 3 times higher than that of the monomer TiO2. XPS, DRS, LSV, and FTIR were used to explore the possible photocatalytic nitrogen fixation mechanism. Studies showed that a close interfacial contact has been formed via the bonding mode of =C-O between the Ti3C2 and TiO2 samples. The formed =C-O bond boosts an oriented photogenerated charge separation and transfer in the Ti3C2/TiO2 composite. This work provides a promising idea for constructing other efficient MXene-based composite photocatalysts for artificial photosynthesis.

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33

Lu, Bao-Fu, Wen-Juan Kang, Shang-Li Shi, Jian Guan, Fang Jing e Bei Wu. "Differences in Fatty Acid and Central Carbon Metabolite Distribution among Different Tissues of Alfalfa–Rhizobia Symbiotic System". Agronomy 14, n. 3 (1 marzo 2024): 511. http://dx.doi.org/10.3390/agronomy14030511.

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Abstract (sommario):

Fatty acid and central carbon metabolism are crucial energy metabolism reactions. However, to date, few studies have examined their distribution characteristics within the alfalfa–rhizobia symbiotic system. To clarify the distributional differences and accumulation rates of fatty acids and central carbon with this system, we measured the plant phenotype, nodule formation, nitrogen fixation capacity, and key nitrogen metabolism enzyme activities of Medicago sativa ‘Gannong No. 9’ 35 days post-inoculation (dpi) with Sinorhizobia meliloti LL11. Additionally, we employed targeted metabolomics to analyze central carbon and fatty acid metabolites in various tissue samples of symbiotic and control (C.K.) plants, as well as in S. meliloti LL11. We found that plant height; root length; aboveground fresh and dry weights; underground fresh and dry weights; and nitrate reductase, nitrogen reductase, glutamine synthetase, and glutamate synthase activities were significantly higher in the leaves and roots of symbiotic plants than in those of C.K. plants. Compared to symbiotic plants, C.K. plants exhibited higher total central carbon and fatty acid metabolite content, accounting for 38.61% and 48.17% of C.K. plants, respectively. We detected 32 central carbon and 40 fatty acid metabolites in S. meliloti LL11, with succinate (343,180.8603 ng·mL−1) and hexadecanoic acid (4889.7783 ng·mL−1) being the most. In both symbiotic and C.K. plants, central carbon metabolite was considerably higher than the fatty acid metabolite central. Moreover, the carbon metabolites found in symbiotic plants were primarily distributed in pink nodule roots (PNRs), with malate exhibiting the highest content (4,800,612.3450 ng·g−1), accounting for 53.09% of total central carbon metabolite content. Fatty acid metabolites were mainly found in pink root nodules (P.N.s), which are sites of nitrogen fixation. Trans-10-nonadecenoic acid and hexadecanoic acid exhibited the highest contents, comprising >15% of the total fatty acid metabolite content. We found that petroselaidic acid is only present in P.N., which seems to be closely related to the nitrogen fixation reaction in P.N. In general, symbiotic plants transfer central carbon metabolites to nodules via PNRs to drive nitrogen fixation. However, in P.N.s, these metabolites are limited, leading to accumulation in PNRs. Fatty acid metabolites, crucial for nitrogen fixation, are prevalent in P.N.s. Conversely, C.K. plants without nitrogen fixation distribute these metabolites primarily to the stems, emphasizing growth. This study provides new insights into the energy metabolism of symbiotic nitrogen fixation.

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34

Villegas, Daniel M., Jaime Velasquez, Jacobo Arango, Karen Obregon, Idupulapati M. Rao, Gelber Rosas e Astrid Oberson. "Urochloa Grasses Swap Nitrogen Source When Grown in Association with Legumes in Tropical Pastures". Diversity 12, n. 11 (5 novembre 2020): 419. http://dx.doi.org/10.3390/d12110419.

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Abstract (sommario):

The degradation of tropical pastures sown with introduced grasses (e.g., Urochloa spp.) has dramatic environmental and economic consequences in Latin America. Nitrogen (N) limitation to plant growth contributes to pasture degradation. The introduction of legumes in association with grasses has been proposed as a strategy to improve N supply via symbiotic N2 fixation, but the fixed N input and N benefits for associated grasses have hardly been determined in farmers’ pastures. We have carried out on-farm research in ten paired plots of grass-alone (GA) vs. grass-legume (GL) pastures. Measurements included soil properties, pasture productivity, and sources of plant N uptake using 15N isotope natural abundance methods. The integration of legumes increased pasture biomass production by about 74%, while N uptake was improved by two-fold. The legumes derived about 80% of their N via symbiotic N2 fixation. The isotopic signature of N of grasses in GA vs. GL pastures suggested that sources of grass N are affected by sward composition. Low values of δ15N found in some grasses in GA pastures indicate that they depend, to some extent, on N from non-symbiotic N2 fixation, while δ15N signatures of grasses in GL pastures pointed to N transfer to grass from the associated legume. The role of different soil–plant processes such as biological nitrification inhibition (BNI), non-symbiotic N2 fixation by GA pastures and legume–N transfer to grasses in GL pastures need to be further studied to provide a more comprehensive understanding of N sources supporting the growth of grasses in tropical pastures.

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35

Adhami Sayad Mahaleh, Moazameh, Mehrnoush Narimisa, Anton Nikiforov, Mikhail Gromov, Yury Gorbanev, Rim Bitar, Rino Morent e Nathalie De Geyter. "Nitrogen Oxidation in a Multi-Pin Plasma System in the Presence and Absence of a Plasma/Liquid Interface". Applied Sciences 13, n. 13 (28 giugno 2023): 7619. http://dx.doi.org/10.3390/app13137619.

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Abstract (sommario):

The recent energy crisis revealed that there is a strong need to replace hydrocarbon-fueled industrial nitrogen fixation processes by alternative, more sustainable methods. In light of this, plasma-based nitrogen fixation remains one of the most promising options, considering both theoretical and experimental aspects. Lately, plasma interacting with water has received considerable attention in nitrogen fixation applications as it can trigger a unique gas- and liquid-phase chemistry. Within this context, a critical exploration of plasma-assisted nitrogen fixation with or without water presence is of great interest with an emphasis on energy costs, particularly in plasma reactors which have potential for large-scale industrial application. In this work, the presence of water in a multi-pin plasma system on nitrogen oxidation is experimentally investigated by comparing two pulsed negative DC voltage plasmas in metal–metal and metal–liquid electrode configurations. The plasma setups are designed to create similar plasma properties, including plasma power and discharge regime in both configurations. The system energy cost is calculated, considering nitrogen-containing species generated in gas and liquid phases as measured by a gas analyzer, nitrate sensor, and a colorimetry method. The energy cost profile as a function of specific energy input showed a strong dependency on the plasma operational frequency and the gas flow rate, as a result of different plasma operation regimes and initiated reverse processes. More importantly, the presence of the plasma/liquid interface increased the energy cost up to 14 ± 8%. Overall, the results showed that the presence of water in the reaction zone has a negative impact on the nitrogen fixation process.

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36

Ronson, C. W., e W. L. Lowther. "Issues affecting the competitiveness of white clover rhizobia in New Zealand pastures". NZGA: Research and Practice Series 6 (1 gennaio 1996): 87–90. http://dx.doi.org/10.33584/rps.6.1995.3364.

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Abstract (sommario):

Research into improving symbiotic nitrogen fixation of white clover in New Zealand pastures through the introduction of effective rhizobia is reviewed. Naturalised populations of rhizobia are usually highly diverse and of reduced effectiveness compared to inoculant strains, and large increases in nitrogen fixed have been found in situations where high nodule occupancy by an inoculant strain was obtained. The likelihood of an inoculant strain initially forming a high proportion of nodules is dependent on the size of the naturalised and inoculant populations, and the strain of rhizobia. Lack of persistence of the inoculant strain in competition with naturalised rhizobia also limits improvement of symbiotic nitrogen fixation in pasture through inoculation. Recent studies suggest that genetic instability of inoculant strains and exchange of symbiotic plasmids contribute to the diversity of naturalised populations and lack of inoculant persistence. Therefore, it is necessary to understand the ecology of naturalised populations, including their genetic interactions with inoculant strains, in order to develop strategies to improve the competitiveness and persistence of inoculant strains. Alternatively it may be possible to increase the effectiveness of indigenous populations through gene transfer from the inoculant strain. The possibility of breeding specific host cultivar/rhizobial strain combinations also merits further research. Keywords: competition, genetic stability, inoculation, nitrogen fixation, rhizobia, white clover

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37

Mulholland, M. R. "The fate of new production from N<sub>2</sub> fixation". Biogeosciences Discussions 3, n. 4 (19 luglio 2006): 1049–80. http://dx.doi.org/10.5194/bgd-3-1049-2006.

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Abstract (sommario):

Abstract. While we now know that marine N2 fixation is a significant source of new nitrogen (N) in the marine environment, little is known about the fate of this production, despite the importance of diazotrophs to global carbon and nutrient cycles. Specifically, does new production from N2 fixation fuel autotrophic or heterotrophic growth, facilitate carbon (C) export from the euphotic zone, or contribute primarily to microbial productivity and respiration in the euphotic zone? For Trichodesmium, the diazotroph we know the most about, the transfer of recently fixed N2 (and C) appears to be primarily through dissolved pools. The release of N appears to vary among and within populations and, probably as a result of the changing physiological state of cells and populations. The net result of trophic transfers appears to depend on the complexity of the colonizing community and co-occurring organisms. In order to understand the impact of diazotrophy on carbon flow and export in marine systems, we need a better assessment of the trophic flow of elements in Trichodesmium communities dominated by different species, various free and colonial morphologies, and in various defined physiological states. Nitrogen and carbon fixation rates themselves vary by orders of magnitude within and among studies highlighting the difficulty in extrapolating global rates of N2 fixation from direct measurements. Because the stoichiometry of N2 and C fixation does not appear to be in balance with the stoichiometry of particles, and the relationship between C and N2 fixation rates is also variable, it is equally difficult to derive global rates of one from the other. A better understanding of the physiology and physiological ecology of Trichodesmium and other marine diazotrophs is necessary to understand and predict the effects of increased or decreased diazotrophy in the context of the carbon cycle and global change.

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38

Crook, Matthew B., Daniel P. Lindsay, Matthew B. Biggs, Joshua S. Bentley, Jared C. Price, Spencer C. Clement, Mark J. Clement, Sharon R. Long e Joel S. Griffitts. "Rhizobial Plasmids That Cause Impaired Symbiotic Nitrogen Fixation and Enhanced Host Invasion". Molecular Plant-Microbe Interactions® 25, n. 8 (agosto 2012): 1026–33. http://dx.doi.org/10.1094/mpmi-02-12-0052-r.

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Abstract (sommario):

The genetic rules that dictate legume-rhizobium compatibility have been investigated for decades, but the causes of incompatibility occurring at late stages of the nodulation process are not well understood. An evaluation of naturally diverse legume (genus Medicago) and rhizobium (genus Sinorhizobium) isolates has revealed numerous instances in which Sinorhizobium strains induce and occupy nodules that are only minimally beneficial to certain Medicago hosts. Using these ineffective strain-host pairs, we identified gain-of-compatibility (GOC) rhizobial variants. We show that GOC variants arise by loss of specific large accessory plasmids, which we call HR plasmids due to their effect on symbiotic host range. Transfer of HR plasmids to a symbiotically effective rhizobium strain can convert it to incompatibility, indicating that HR plasmids can act autonomously in diverse strain backgrounds. We provide evidence that HR plasmids may encode machinery for their horizontal transfer. On hosts in which HR plasmids impair N fixation, the plasmids also enhance competitiveness for nodule occupancy, showing that naturally occurring, transferrable accessory genes can convert beneficial rhizobia to a more exploitative lifestyle. This observation raises important questions about agricultural management, the ecological stability of mutualisms, and the genetic factors that distinguish beneficial symbionts from parasites.

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39

Bolhuis, Henk, Ina Severin, Veronique Confurius-Guns, Ute I. A. Wollenzien e Lucas J. Stal. "Horizontal transfer of the nitrogen fixation gene cluster in the cyanobacterium Microcoleus chthonoplastes". ISME Journal 4, n. 1 (10 settembre 2009): 121–30. http://dx.doi.org/10.1038/ismej.2009.99.

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40

Okereke, G. U., e D. Anyama. "Growth, Nitrogen Fixation and Transfer in a Mixed Cropping System of Cowpea-Rice". Biological Agriculture & Horticulture 9, n. 1 (gennaio 1992): 65–76. http://dx.doi.org/10.1080/01448765.1992.9754617.

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41

Valdés, Jorge H., Inti Pedroso, Raquel Quatrini, Kevin B. Hallberg, Pablo D. T. Valenzuela e David S. Holmes. "Insights into the Metabolism and Ecophysiology of Three Acidithiobacilli by Comparative Genome Analysis". Advanced Materials Research 20-21 (luglio 2007): 439–42. http://dx.doi.org/10.4028/www.scientific.net/amr.20-21.439.

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Abstract (sommario):

Draft genome sequences of Acidithiobacillus thiooxidans ATCC 19377 and A. caldus ATCC 51756 have been annotated. Bioinformatic analysis of these two new genomes, together with that of A. ferrooxidans ATCC 23270, allows the prediction of metabolic and regulatory models for each species and has provided a unique opportunity to undertake comparative genomic studies of this group of bioleaching bacteria. In this paper, we report preliminary information on metabolic and electron transfer pathways for ten characteristics of the three acidithiobacilli: CO2 fixation, the TCA cycle, sulfur oxidation, sulfur reduction, iron oxidation, iron assimilation, hydrogen oxidation, flagella formation, Che signaling (chemotaxis) and nitrogen fixation. Predicted transcriptional and metabolic interplay between pathways pinpoints potential coordinated responses to environmental signals such as energy source, oxygen and nutrient limitations. The predicted pathway for nitrogen fixation in A. ferrooxidans will be described as an example of such an integrated response. Several responses appear to be especially characteristic of autotrophic microorganisms and may have direct implications for metabolic processes of critical relevance to the understanding of how these microorganisms survive and proliferate in extreme environments, including industrial bioleaching operations.

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42

Wang, Libo, Mohan Li, Shiyu Wang, Tingting Zhang, Fengyan Li e Lin Xu. "Enhanced photocatalytic nitrogen fixation in BiVO₄: constructing oxygen vacancies and promoting electron transfer through Ohmic contact". New Journal of Chemistry 45, n. 47 (2021): 22234–42. http://dx.doi.org/10.1039/d1nj04580f.

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Abstract (sommario):

The Ag nanoparticles deposited on the surface of BiVO4 containing oxygen vacancies are employed in photocatalytic N2 fixation. The NH3 generation rate is enhanced by constructing abundant oxygen vacancies and promoting electron transfer by Ohmic contact.

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43

Ding, Hao, e Michael F. Hynes. "Plasmid transfer systems in the rhizobia". Canadian Journal of Microbiology 55, n. 8 (agosto 2009): 917–27. http://dx.doi.org/10.1139/w09-056.

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Abstract (sommario):

Rhizobia are agriculturally important bacteria that can form nitrogen-fixing nodules on the roots of leguminous plants. Agricultural application of rhizobial inoculants can play an important role in increasing leguminous crop yields. In temperate rhizobia, genes involved in nodulation and nitrogen fixation are usually located on one or more large plasmids (pSyms) or on symbiotic islands. In addition, other large plasmids of rhizobia carry genes that are beneficial for survival and competition of rhizobia in the rhizosphere. Conjugative transfer of these large plasmids thus plays an important role in the evolution of rhizobia. Therefore, understanding the mechanism of conjugative transfer of large rhizobial plasmids provides foundations for maintaining, monitoring, and predicting the behaviour of these plasmids during field release events. In this minireview, we summarize two types of known rhizobial conjugative plasmids, including quorum sensing regulated plasmids and RctA-repressed plasmids. We provide evidence for the existence of a third type of conjugative plasmid, including pRleVF39c in Rhizobium leguminosarum bv. viciae strain VF39SM, and we provide a comparison of the different types of conjugation genes found in members of the rhizobia that have had their genomes sequenced so far.

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44

Sprent, J. I., e J. A. Raven. "Evolution of nitrogen-fixing symbioses". Proceedings of the Royal Society of Edinburgh. Section B. Biological Sciences 85, n. 3-4 (1985): 215–37. http://dx.doi.org/10.1017/s0269727000004036.

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Abstract (sommario):

SynopsisBecause of both the energy costs and the slowness of the reactions of the nitrogenase complex compared with those involving some form of combined nitrogen (oxidised or reduced), we argue that the evolution of nitrogen-fixing organisms required an environment which was very limited in combined nitrogen. This is thought to have occurred after phototrophy evolved, but before water was used as a hydrogen donor (and therefore oxygen was present in the atmosphere). After oxygenic photosynthesis evolved, the need for a high level of biological nitrogen-fixation remained, since abiotic inputs were insufficient to keep pace with the rapidly evolving biomass (flora and fauna). Symbiotic fixation probably first evolved in the form of casual associations between cyanobacteria and most other groups of plants. By inhabiting the sporophytic generation of evolving land plants (cycads in particular), protection against nitrogenase-inactivating oxygen and a more desiccating environment was achieved simultaneously.We envisage nodulated plants arising by the transfer ofnifgenes into tumour-forming bacteria. In the case of legumes, these would be ancestors of extant agrobacteria, which gain entry into their hostsviawounds. Co-evolution of symbionts from nitrogen-fixing tumours has taken several routes, leading to extant nodules differing in mode of infection, structure and physiology. Evolution towards optimisation of oxygen usage is continuing.Nitrogen-fixing symbiosis in animal systems is only advantageous in specialised ecological niches in which wood is the sole dietary intake. In the case of shipworms, the symbiosis has many of the advanced features associated with nitrogen fixing root nodules.

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45

Лазарев, Н. Н., О. В. Кухаренкова, С. М. Авдеев, Е. М. Куренкова e С. А. Дикарева. "Symbiotic nitrogen fixation by perennial legumes in meadow ecosystems". Кормопроизводство, n. 2.2022 (25 aprile 2022): 20–28. http://dx.doi.org/10.25685/krm.2022.2.2022.002.

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Abstract (sommario):

В научном обзоре представлены результаты российских и зарубежных исследований по азотфиксирующей способности многолетних бобовых трав. Благодаря способности фиксировать атмосферный азот многолетние бобовые травы являются наиболее выгодными кормовыми культурами, обеспечивающими получение дешёвых кормов с высоким содержанием сырого протеина, дефицит которого ощущается в кормопроизводстве нашей страны. Фиксация и ассимиляция азота сопоставима для растений по своей значимости с фотосинтезом. В среднем за сезон многолетние бобовые травы фиксируют от 92 до 180 кг/га атмосферного азота. В Российской Федерации многолетние бобовые травы, произрастающие на сеяных и естественных угодьях, по количеству фиксируемого азота значительно превосходят другие бобовые культуры. В луговых агрофитоценозах бобовые травы могут передавать злакам до 34% фиксированного азота. Размеры азотфиксации зависят от кислотности и обеспеченности почвы минеральным азотом и влагой. Повышенная кислотность почвы способствует повышению токсичного действия подвижного алюминия и марганца и снижению обеспеченности молибденом и кобальтом. Особенно плохо переносят повышенную кислотность ризобии вида Sinorhizobium meliloti, которые вступают в симбиоз с люцерной. Внесение азотных удобрений обычно также отрицательно сказывается на фиксации азота. Среди бобовых растений выделяются узко- и широко специфичные хозяева. Ризобии вида Rhizobium galegae вступают в симбиоз только с растениями козлятника, Sinorhizobium meliloti — с люцерной, донником и пажитником, Rhizobium leguminosarum biovar trifolii — с клеверами, Mezorhizobium loti — c лядвенцем, люпином, язвенником. Инокуляция семян бобовых трав высокоэффективными штаммами клубеньковых бактерий повышает урожайность на 11–32%. Сортомикробные системы на основе новых сортов бобовых культур обладают повышенной адаптивностью и способны обеспечивать прибавки урожая не менее 50%. This review is focused on Russian and foreign investigations of nitrogen-fixing ability of perennial legumes. Due to such a property, perennial legumes are the most beneficial forage crops providing cheap feed with high content of valuable crude protein. Nitrogen fixation and assimilation are as important as photosynthesis.On the average perennial legumes fix from 92 to 180 kg ha-1 of atmospheric nitrogen. In Russia perennial legumes growing on farm and natural lands significantly exceed other legumes in nitrogen fixed. In grassland ecosystems legumes transfer up to 34% of fixed nitrogen to gramineous. The effectiveness of nitrogen fixation is affected by soil pH and availability of water and mineral nitrogen. High pH leads to toxic effect of soluble aluminum and manganese and deficiency in molybdenum and cobalt. Sinorhizobium meliloti forming symbiosis with alfalfa significantly suffer from high pH in particular. Nitrogen fertilizers negatively impact nitrogen fixation. Some strains of nodule bacteria have broad host range while other show high specificity only to one plant. For instance, Rhizobium galegae are compatible only with eastern goat’s rue, Sinorhizobium meliloti — alfalfa, melilot and fenugreek, Rhizobium leguminosarum biovar trifolii — clover, Mezorhizobium loti — birdʼs-foot trefoil, lupine, Anthyllis spp. Seed inoculation with highly effective strains of nodule bacteria increases legume yield by 11–32%. New variety-symbiont systems show high resistance to local conditions and provide yield increase of at least 50%.

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Makita, Takashi, Kazumi Hirabara e Haruko Hirose. "Combination of cryo-SEM and WET-SEM". Proceedings, annual meeting, Electron Microscopy Society of America 45 (agosto 1987): 568–69. http://dx.doi.org/10.1017/s0424820100127360.

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Abstract (sommario):

WET-SEM is a version of commercially available SEM equipped with Robinson's type of wide-angle backscattered electron detector to observe wet samples under low vacuum(0.3-0.5 torr) and it has been used to variable biological samples with or without chemical fixation. Its versatility to observe hydrated specimens without any metalic coating is obviously advantageous to application of cryo-SEM to biological samples.Recent improvement of nitrogen gas cooled cold stage, and vacuum transfer device(Hexland, England) made the WET-SEM(ISI, Akashi, Japan) as a tool for quick survey of unfixed, hydrated, uncoated, and frozen fractured tissue blocks of animals. For examples, tissue from the rat liver or the mice kidney was quickly frozen in nitrogen slush for several minutes and then transfered to prechamber with a type of vacuum transfer system. Within the prechamber the surface of frozen sample is sublimated or fractured under vacuum and then the sample is ready to be seen on the cryo stage which is cooled by nitrogen gas.

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Yu, Qiming, e Hongming Wang. "Efficient dinitrogen fixation on porous covalent organic framework/carbon nanotubes hybrid at low overpotential". Functional Materials Letters 14, n. 05 (11 giugno 2021): 2151027. http://dx.doi.org/10.1142/s1793604721510279.

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Abstract (sommario):

Electrocatalytic nitrogen reduction under ambient conditions is a promising approach for ammonia synthesis, but it is challenging to develop highly efficient electrocatalysts. In this work, a hybrid of covalent organic framework (COF) and carbon nanotubes (CNTs) are developed for efficient nitrogen electroreduction with a high faradaic efficiency (FE) of 12.7% at 0.0 V versus reversible hydrogen electrode (RHE) and a remarkable production rate of ammonia up to 8.56 [Formula: see text]g h[Formula: see text] mg[Formula: see text] at –0.2 V versus RHE. Experiments and theoretical calculations reveal that Ni centers are active sites for NH3 synthesis, while the [Formula: see text]–[Formula: see text] stacking between COF-366-Ni and conductive CNTs scaffold results in the rapid interfacial charge transfer. This investigation provides new insights on the rational design of organic–inorganic porous hybrids for efficient nitrogen conversion and ammonia synthesis at ambient conditions.

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Caffin, Mathieu, Hugo Berthelot, Véronique Cornet-Barthaux, Aude Barani e Sophie Bonnet. "Transfer of diazotroph-derived nitrogen to the planktonic food web across gradients of N<sub>2</sub> fixation activity and diversity in the western tropical South Pacific Ocean". Biogeosciences 15, n. 12 (21 giugno 2018): 3795–810. http://dx.doi.org/10.5194/bg-15-3795-2018.

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Abstract (sommario):

Abstract. Biological dinitrogen (N2) fixation provides the major source of new nitrogen (N) to the open ocean, contributing more than atmospheric deposition and riverine inputs to the N supply. Yet the fate of the diazotroph-derived N (DDN) in the planktonic food web is poorly understood. The main goals of this study were (i) to quantify how much of DDN is released to the dissolved pool during N2 fixation and how much is transferred to bacteria, phytoplankton and zooplankton, and (ii) to compare the DDN release and transfer efficiencies under contrasting N2 fixation activity and diversity in the oligotrophic waters of the western tropical South Pacific (WTSP) Ocean. We used nanometre-scale secondary ion mass spectrometry (nanoSIMS) coupled with 15N2 isotopic labelling and flow cytometry cell sorting to track the DDN transfer to plankton, in regions where the diazotroph community was dominated by either Trichodesmium or by UCYN-B. After 48 h, ∼ 20–40 % of the N2 fixed during the experiment was released to the dissolved pool when Trichodesmium dominated, while the DDN release was not quantifiable when UCYN-B dominated; ∼ 7–15 % of the total fixed N (net N2 fixation + release) was transferred to non-diazotrophic plankton within 48 h, with higher transfer efficiencies (15 ± 3 %) when UCYN-B dominated as compared to when Trichodesmium dominated (9 ± 3 %). The pico-cyanobacteria Synechococcus and Prochlorococcus were the primary beneficiaries of the DDN transferred (∼ 65–70 %), followed by heterotrophic bacteria (∼ 23–34 %). The DDN transfer in bacteria was higher (34 ± 7 %) in the UCYN-B-dominating experiment compared to the Trichodesmium-dominating experiments (24 ± 5 %). Regarding higher trophic levels, the DDN transfer to the dominant zooplankton species was less efficient when the diazotroph community was dominated by Trichodesmium (∼ 5–9 % of the DDN transfer) than when it was dominated by UCYN-B (∼ 28 ± 13 % of the DDN transfer). To our knowledge, this study provides the first quantification of DDN release and transfer to phytoplankton, bacteria and zooplankton communities in open ocean waters. It reveals that despite UCYN-B fix N2 at lower rates compared to Trichodesmium in the WTSP, the DDN from UCYN-B is much more available and efficiently transferred to the planktonic food web than the DDN originating from Trichodesmium.

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Han, Yunlei, Na Lu, Qinghua Chen, Yuhua Zhan, Wei Liu, Wei Lu, Baoli Zhu, Min Lin, Zhirong Yang e Yongliang Yan. "Interspecies Transfer and Regulation of Pseudomonas stutzeri A1501 Nitrogen Fixation Island in Escherichia coli". Journal of Microbiology and Biotechnology 25, n. 8 (28 agosto 2015): 1339–48. http://dx.doi.org/10.4014/jmb.1502.02027.

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Farnham, D. E., e J. R. George. "Harvest Management Effects on Dinitrogen Fixation and Nitrogen Transfer in Red Clover-Orchardgrass Mixtures". Journal of Production Agriculture 7, n. 3 (luglio 1994): 360–64. http://dx.doi.org/10.2134/jpa1994.0360.

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