Showing papers on "Nitrogen fixation published in 2022"
TL;DR: In this article , the authors show that the overlap in both the signaling pathways and downstream infection components of these symbioses reflects their evolutionary relatedness and the common requirements of these two interactions.
Abstract: Most land plants benefit from endosymbiotic interactions with mycorrhizal fungi, including legumes and some nonlegumes that also interact with endosymbiotic nitrogen (N)-fixing bacteria to form nodules. In addition to these helpful interactions, plants are continuously exposed to would-be pathogenic microbes: discriminating between friends and foes is a major determinant of plant survival. Recent breakthroughs have revealed how some key signals from pathogens and symbionts are distinguished. Once this checkpoint has been passed and a compatible symbiont is recognized, the plant coordinates the sequential development of two types of specialized structures in the host. The first serves to mediate infection, and the second, which appears later, serves as sophisticated intracellular nutrient exchange interfaces. The overlap in both the signaling pathways and downstream infection components of these symbioses reflects their evolutionary relatedness and the common requirements of these two interactions. However, the different outputs of the symbioses, phosphate uptake versus N fixation, require fundamentally different components and physical environments and necessitated the recruitment of different master regulators, NODULE INCEPTION-LIKE PROTEINS, and PHOSPHATE STARVATION RESPONSES, for nodulation and mycorrhization, respectively.
37 citations
TL;DR: This work has shown that once a checkpoint has been passed and a compatible symbiont is recognized, the plant coordinates the sequential development of two types of specialized structures in the host, which serve to mediate infection and serve as sophisticated intracellular nutrient exchange interfaces.
Abstract: Most land plants benefit from endosymbiotic interactions with mycorrhizal fungi, including legumes and some non-legumes that also interact with endosymbiotic nitrogen-fixing bacteria to form nodules. In addition to these helpful interactions, plants are continuously exposed to would-be pathogenic microbes: discriminating between friends and foes is a major determinant of plant survival. Recent breakthroughs have revealed how some key signals from pathogens and symbionts are distinguished. Once this checkpoint has been passed and a compatible symbiont is recognized, the plant coordinates the sequential development of two types of specialized structures in the host. The first serve to mediate infection, and the second, which appear later, serve as sophisticated intracellular nutrient exchange interfaces. The overlap in both the signaling pathways and downstream infection components of these symbioses reflects their evolutionary relatedness and the common requirements of these two interactions. However, the different outputs of the symbioses, phosphate uptake vs. nitrogen fixation, require fundamentally different components and physical environments and necessitated the recruitment of different master regulators, NLPs and PHRs, for nodulation and mycorrhization, respectively.
37 citations
TL;DR: In this paper , As-dependent BNF was detected in cultures inoculated from As-rich tailing samples derived from the Xikuangshan mining area in China, as suggested by nitrogenase activity assays, quantitative polymerase chain reaction, and 15N2 enrichment incubations.
Abstract: Biological nitrogen fixation (BNF) has important environmental implications in tailings by providing bioavailable nitrogen to these habitats and sustaining ecosystem functions. Previously, chemolithotrophic diazotrophs that dominate in mine tailings were shown to use reduced sulfur (S) as the electron donor. Tailings often contain high concentrations of As(III) that might function as an alternative electron donor to fuel BNF. Here, we tested this hypothesis and report on BNF fueled by As(III) oxidation as a novel biogeochemical process in addition to BNF fueled by S. Arsenic (As)-dependent BNF was detected in cultures inoculated from As-rich tailing samples derived from the Xikuangshan mining area in China, as suggested by nitrogenase activity assays, quantitative polymerase chain reaction, and 15N2 enrichment incubations. As-dependent BNF was also active in eight other As-contaminated tailings and soils, suggesting that the potential for As-dependent BNF may be widespread in As-rich habitats. DNA-stable isotope probing identified Serratia spp. as the bacteria responsible for As-dependent BNF. Metagenomic binning indicated that the essential genes for As-dependent BNF [i.e., nitrogen fixation, As(III) oxidation, and carbon fixation] were present in Serratia-associated metagenome-assembled genomes. Over 20 Serratia genomes obtained from NCBI also contained essential genes for both As(III) oxidation and BNF (i.e., aioA and nifH), suggesting that As-dependent BNF may be a widespread metabolic trait in Serratia spp.
33 citations
TL;DR: In this article , the authors summarized the recent advances in materials sciences for photocatalytic nitrogen fixation and proposed an alternative for artificial ammonia synthesis and coupling reactions with other reactions for the synthesis of other high-value chemicals.
Abstract: The traditional synthesis of ammonia is an industrial process with high energy consumption that is not environmentally friendly; thus, it is urgent to develop cost-effective approaches to synthesize ammonia under ambient conditions. In recent years, the photochemical synthesis of ammonia has become a hot research frontier. In this mini review, we summarize the recent advances in materials sciences for photocatalytic nitrogen fixation. Beyond nitrogen fixation, we talk about an alternative for artificial ammonia synthesis and coupling reactions with other reactions for the synthesis of other high-value chemicals. The results and findings of this review will help the development of ammonia synthesis and the synthesis of other high-value chemicals.
33 citations
TL;DR: In this paper , a heterojunction-based photocatalytic system is designed to achieve all nitrogen fixation, a sustainable and simultaneous conversion of N2 molecules into ammonia and nitrate products under mild conditions.
Abstract: Ammonia and nitrates are the most fundamental and significant raw ingredients in human society. Till now, industrial synthetic ammonia by Haber–Bosch process and industrial synthetic nitrates by the Ostwald process have encountered increasingly serious challenges, i.e., high energy consumption, high cost, and environment‐harmful gas emissions. Therefore, developing alternative approaches to achieve nitrogen fixation to overcome the inherent deficiencies of the well‐established Haber–Bosch and Ostwald processes has fascinated scientists for many years, especially the simultaneous formation of ammonia and nitrate directly from N2 molecules, which has been rarely studied. Herein, a heterojunction‐based photocatalytic system is designed to successfully achieve “overall nitrogen fixation,” a sustainable and simultaneous conversion of N2 molecules into ammonia and nitrate products under mild conditions. In this heterojunction, interfacial charge redistribution (ICR) promotes selective accumulations of photogenerated electrons and holes in the CdS and WO3 components. As a result, N2 molecules can be activated and reduced to ammonia products with yields of 35.8 µmol h−1 g−1 by a multi‐electron process, and synchronously oxidized into nitrate products with yields of 14.2 µmol h−1 g−1 by a hole‐induced oxidation coupling process. This work provides a novel insight and promising approach to realize artificial nitrogen fixation under mild condition.
31 citations
TL;DR: 30 shallows freshwater lakes in the eastern plain of China were selected to measure dissolved N2 and Ar concentrations through N2: Ar method using a membrane inlet mass spectrometer to quantify the nitrogen fixation capacities and investigate whether the temperature and water residence time have a great impact on nitrogen fixation.
Abstract: Eutrophication and harmful cyanobacterial blooms threaten water resources all over the world. There is a great controversy about controlling only phosphorus or controlling both nitrogen and phosphorus in the management of lake eutrophication. The primary argument against the dual nutrients control of eutrophication is that nitrogen fixation can compensate the nitrogen deficits. Thus, it is of great necessary to study the factors that can significantly affect the nitrogen fixation. Due to the difference of climate and human influence, the water quality of different lakes (such as water temperature, N:P ratio and water residence time) is also quite different. Numerous studies have reported that the low N:P ratio can intensify the nitrogen fixation capacities. However, the effects of temperature and water residence time on the nitrogen fixation remain unclear. Thus, 30 shallows freshwater lakes in the eastern plain of China were selected to measure dissolved N2 and Ar concentrations through N2: Ar method using a membrane inlet mass spectrometer to quantify the nitrogen fixation capacities and investigate whether the temperature and water residence time have a great impact on nitrogen fixation. The results have shown that the short lake water residence time can severely inhibit the nitrogen fixation capacities through inhibiting the growth of nitrogen-fixing cyanobacteria, changing the N:P ratio and resuspending the solids from sediments. Similarly, lakes with low water temperature also have a low nitrogen fixation capacity, suggesting that controlling nitrogen in such lakes is feasible if the growth of cyanobacteria is limited by nitrogen.
30 citations
TL;DR: In this article , the authors showed that the Fe atoms in Mo3S4Fe cubes can capture a N2 molecule and catalyse N2 silylation to form N(SiMe3)3 under treatment with excess sodium and trimethylsilyl chloride.
Abstract: Nitrogen (N2) fixation by nature, which is a crucial process for the supply of bio-available forms of nitrogen, is performed by nitrogenase. This enzyme uses a unique transition-metal-sulfur-carbon cluster as its active-site co-factor ([(R-homocitrate)MoFe7S9C], FeMoco)1,2, and the sulfur-surrounded iron (Fe) atoms have been postulated to capture and reduce N2 (refs. 3-6). Although there are a few examples of synthetic counterparts of the FeMoco, metal-sulfur cluster, which have shown binding of N2 (refs. 7-9), the reduction of N2 by any synthetic metal-sulfur cluster or by the extracted form of FeMoco10 has remained elusive, despite nearly 50 years of research. Here we show that the Fe atoms in our synthetic [Mo3S4Fe] cubes11,12 can capture a N2 molecule and catalyse N2 silylation to form N(SiMe3)3 under treatment with excess sodium and trimethylsilyl chloride. These results exemplify the catalytic silylation of N2 by a synthetic metal-sulfur cluster and demonstrate the N2-reduction capability of Fe atoms in a sulfur-rich environment, which is reminiscent of the ability of FeMoco to bind and activate N2.
29 citations
TL;DR: In this paper , the authors investigate the abundance, activity, and drivers of nitrogenfixing diazotrophs across the tropical western North Pacific and find a basin-scale coherence of D2 abundances and N2 fixation rates with the supply ratio of iron:nitrogen to the upper ocean.
Abstract: Nitrogen fixation is critical for the biological productivity of the ocean, but clear mechanistic controls on this process remain elusive. Here, we investigate the abundance, activity, and drivers of nitrogen-fixing diazotrophs across the tropical western North Pacific. We find a basin-scale coherence of diazotroph abundances and N2 fixation rates with the supply ratio of iron:nitrogen to the upper ocean. Across a threshold of increasing supply ratios, the abundance of nifH genes and N2 fixation rates increased, phosphate concentrations decreased, and bioassay experiments demonstrated evidence for N2 fixation switching from iron to phosphate limitation. In the northern South China Sea, supply ratios were hypothesized to fall around this critical threshold and bioassay experiments suggested colimitation by both iron and phosphate. Our results provide evidence for iron:nitrogen supply ratios being the most important factor in regulating the distribution of N2 fixation across the tropical ocean.
26 citations
TL;DR: In this paper , a review of the fundamental processes used by Pseudomonas spp. to promote plant development and reduce environmental stresses is presented, and the presence of potential genes in the genome of different pseudomonas strains is discussed.
Abstract: ABSTRACT The widespread use of biofertilizers, rather than chemical fertilizers, is significantly more likely to accomplish sustainable agriculture production globally. Plant growth-promoting rhizobacteria (PGPR) are chemical-free alternatives to conventional crop protection in agriculture. Pseudomonas spp. are unique among the PGPR genera in terms of root colonization, nitrogen fixation, production of exopolysaccharides, siderophores, hydrogen cyanide (HCN), and phytohormones, solubilization of phosphorus, potassium, and zinc, biofilm formation, antioxidant activities, stress adaptation abilities, and positive interactions with other microbial communities. They also aid plant development by promoting biotic and abiotic stress tolerance, as well as supporting host plant nutrition. Pseudomonas is regarded as an environmentally acceptable alternative to harmful chemical fertilizers because of its active growth-promoting actions. However, to achieve this goal, workers must first get a complete understanding of the numerous processes used by Pseudomonas, allowing them to fully exploit the bacteria potential in the future. Therefore, the present review has been undertaken to discuss the fundamental processes used by Pseudomonas spp. to promote plant development and reduce environmental stresses. In addition, we described some reported Pseudomonas-based biofertilizers worldwide and the presence of potential genes in the genome of different Pseudomonas strains to understand the mechanism of Pseudomonas mediated plant growth promotion at the molecular level.
24 citations
TL;DR: In this article , a dehydrated Zr-based MOF UiO-66(SH) 2 was used as a visible light driven photocatalyst to mimic the biological N 2 fixation process.
Abstract: This work reports a dehydrated Zr-based MOF UiO-66(SH) 2 as a visible light driven photocatalyst to mimic the biological N 2 fixation process. The 15 N 2 and other control-experiments demonstrated that the new photocatalyst is highly efficient in converting N 2 to ammonia. In-situ TGA, XPS, EXAFS etc. and first-principles simulations were used to demonstrate the role of the thermal treatment and the changes of the local structures around Zr due to the dehydration. It was shown that the dehydration opened a gate for the entry of N 2 molecules into the [Zr 6 O 6 ] cluster where the strong N≡N bond was broken stepwise by μ-N-Zr type interactions driven by the photoelectrons aided by the protonation. This mechanism was discussed in comparison with the Lowe-Thorneley mechanism proposed for the MoFe nitrogenase, and with emphasis on the [Zr 6 O 6 ] cluster effect and the leading role of photoelectrons over the protonation. The results shed new light on understanding the catalytic mechanism of biological N 2 fixation and open a new way to fix N 2 under mild conditions.
24 citations
TL;DR: In this paper , 30 shallows freshwater lakes in the eastern plain of China were selected to measure dissolved N2 and Ar concentrations through N2:Ar method using a membrane inlet mass spectrometer to quantify the nitrogen fixation capacities and investigate whether the temperature and water residence time have a great impact on nitrogen fixation.
Abstract: Eutrophication and harmful cyanobacterial blooms threaten water resources all over the world. There is a great controversy about controlling only phosphorus or controlling both nitrogen and phosphorus in the management of lake eutrophication. The primary argument against the dual nutrients control of eutrophication is that nitrogen fixation can compensate the nitrogen deficits. Thus, it is of great necessary to study the factors that can significantly affect the nitrogen fixation. Due to the difference of climate and human influence, the water quality of different lakes (such as water temperature, N:P ratio and water residence time) is also quite different. Numerous studies have reported that the low N:P ratio can intensify the nitrogen fixation capacities. However, the effects of temperature and water residence time on the nitrogen fixation remain unclear. Thus, 30 shallows freshwater lakes in the eastern plain of China were selected to measure dissolved N2 and Ar concentrations through N2: Ar method using a membrane inlet mass spectrometer to quantify the nitrogen fixation capacities and investigate whether the temperature and water residence time have a great impact on nitrogen fixation. The results have shown that the short lake water residence time can severely inhibit the nitrogen fixation capacities through inhibiting the growth of nitrogen-fixing cyanobacteria, changing the N:P ratio and resuspending the solids from sediments. Similarly, lakes with low water temperature also have a low nitrogen fixation capacity, suggesting that controlling nitrogen in such lakes is feasible if the growth of cyanobacteria is limited by nitrogen.
TL;DR: In this article , the assembly and functions of maize microbiomes across soil types, climate zones, and genotypes were assessed by assessing the stem xylem selectively recruits highly conserved microbes dominated by Gammaproteobacteria.
Abstract: Microbiomes are important for crop performance. However, a deeper knowledge of crop-associated microbial communities is needed to harness beneficial host-microbe interactions. Here, by assessing the assembly and functions of maize microbiomes across soil types, climate zones, and genotypes, we found that the stem xylem selectively recruits highly conserved microbes dominated by Gammaproteobacteria. We showed that the proportion of bacterial taxa carrying the nitrogenase gene (nifH) was larger in stem xylem than in other organs such as root and leaf endosphere. Of the 25 core bacterial taxa identified in xylem sap, several isolated strains were confirmed to be active nitrogen-fixers or to assist with biological nitrogen fixation. On this basis, we established synthetic communities (SynComs) consisting of two core diazotrophs and two helpers. GFP-tagged strains and 15N isotopic dilution method demonstrated that these SynComs do thrive and contribute, through biological nitrogen fixation, 11.8% of the total N accumulated in maize stems. These core taxa in xylem sap represent an untapped resource that can be exploited to increase crop productivity.
TL;DR: In this article , a review of typical layered materials used in nitrogen fixation and categorization of them into metal-containing and metal-free materials is presented, and the strategies, challenges, and prospects for future developments of nitrogen fixation materials at room temperature and pressure are summarized.
TL;DR: This work exploits synthetic transkingdom signaling to establish plant host-specific control of the N2-fixation catalyst nitrogenase in Azorhizobium caulinodans occupying barley roots and demonstrates how partner-specific interactions can be established to avoid potential growth promotion of nontarget plants.
Abstract: Significance Inoculation of cereals with diazotrophic (N2-fixing) bacteria offers a sustainable alternative to the application of nitrogen fertilizers in agriculture. While natural diazotrophs have evolved multilayered regulatory mechanisms that couple N2 fixation with assimilation of the product NH3 and prevent release to plants, genetic modifications can permit excess production and excretion of NH3. However, a lack of stringent host-specificity for root colonization by the bacteria would allow growth promotion of target and nontarget plants species alike. Here, we exploit synthetic transkingdom signaling to establish plant host-specific control of the N2-fixation catalyst nitrogenase in Azorhizobium caulinodans occupying barley roots. This work demonstrates how partner-specific interactions can be established to avoid potential growth promotion of nontarget plants.
TL;DR: In this article , the authors investigated the effects of adding red mud (RM) on denitrification and nitrogen fixation in composting and found that adding RM could reduce nitrogen loss and improve the quality of compost via enhancing nitrogen fixation and inhibiting denitification process.
TL;DR: In this paper , a CRISPR-based gene editing targeting apigenin breakdown in rice was used to increase the production of compounds that stimulated biofilm formation in soil diazotrophic bacteria, promoted bacterial colonization of plant tissues and improved biological nitrogen fixation.
Abstract: Summary Improving biological nitrogen fixation (BNF) in cereal crops is a long‐sought objective; however, no successful modification of cereal crops showing increased BNF has been reported. Here, we described a novel approach in which rice plants were modified to increase the production of compounds that stimulated biofilm formation in soil diazotrophic bacteria, promoted bacterial colonization of plant tissues and improved BNF with increased grain yield at limiting soil nitrogen contents. We first used a chemical screening to identify plant‐produced compounds that induced biofilm formation in nitrogen‐fixing bacteria and demonstrated that apigenin and other flavones induced BNF. We then used CRISPR‐based gene editing targeting apigenin breakdown in rice, increasing plant apigenin contents and apigenin root exudation. When grown at limiting soil nitrogen conditions, modified rice plants displayed increased grain yield. Biofilm production also modified the root microbiome structure, favouring the enrichment of diazotrophic bacteria recruitment. Our results support the manipulation of the flavone biosynthetic pathway as a feasible strategy for the induction of biological nitrogen fixation in cereals and a reduction in the use of inorganic nitrogen fertilizers.
TL;DR: In this paper , a review examines the evolutionary journey that has led to the diversification of legumes, in particular its nitrogen-fixing symbiosis, and asks four questions to investigate which legume traits might have contributed to their success: 1. If nitrogen fixation was a reason for such a success, why have some species lost the symbiosis?
TL;DR: In this article , the authors present the current knowledge of BNF by free-living, non-symbiotic and symbiotic diazotrophs in the global N cycle, examines global and regional estimates of contributions, and discusses possible strategies to enhance BNF for the prospective benefit of cereal N nutrition.
TL;DR: In this paper , a molecular-level post-modification strategy has been explored to integrate diverse alkyl chains on a ferriporphyrin-based metalorganic framework (MOF) PCN-222(Fe), which provides adjustable hydrophobicity and highly dispersed active sites.
Abstract: Electrocatalytic N 2 fixation represents an energy-efficient and long-term sustainable approach, which can convert N 2 to NO 3 – or NH 3 via the electrochemical N 2 oxidation reaction (NOR) or N 2 reduction reaction (NRR). However, the inert N 2 molecule, low activity of electrocatalysts, and predisposed competitive reactions result in the poor yields and Faradaic efficiencies of N 2 fixation reactions, which greatly restrict the application of such green synthesis technology. In this work, a molecular-level post-modification strategy has been explored to integrate diverse alkyl chains on a ferriporphyrin-based metal–organic framework (MOF) PCN-222(Fe), which provides adjustable hydrophobicity and highly dispersed active sites. The increased lengths of alkyl groups can gradually improve the hydrophobicity of decorated MOFs, which effectively suppress the competitive reactions and boost the electrocatalytic NOR and NRR performances. Significantly, the highest Faradaic efficiency of 70.7% so far and a state-of-the-art NO 3 − yield of 110.9 μg h –1 mg cat. –1 can be achieved for NOR, which are attributed to the synergistic effect of FeN 4 active sites, high porosity, and strong hydrophobicity for n -octadecylphosphonic acid (OPA) decorated PCN-222(Fe). The hydrophobicity of ferriporphyrin-based MOF can be modulated using the molecular-level post-modification strategy, which remarkably boosts the electrocatalytic performances for N 2 oxidation to NO 3 – or N 2 reduction to NH 3 under ambient conditions. The highest Faradaic efficiency of 70.7% by far and a state-of-the-art of NO 3 − yield of 110.9 μg h –1 mg cat. –1 are realized for nitrogen oxidation reaction, in virtue of the synergistic effect of ferriporphyrin active sites, high porosity, and enhanced hydrophobicity. • The hydrophobicity of a ferriporphyrin-based MOF can be well modulated by the molecular-level post-modification strategy. • The enhanced hydrophobicity remarkably boosts the electrocatalytic performances for ambient N 2 oxidation or N 2 reduction reaction. • The Faradaic efficiency of 70.7% and a NO 3 − yield of 110.9 μg h –1 mg cat. –1 are realized for nitrogen oxidation reaction.
TL;DR: This review summarizes the beneficial effects of cyanobacterial co-cultivation on plants, highlighting the substances exchanged and the strength of Cyanobacterial symbioses with plants.
Abstract: Cyanobacteria are ubiquitous phototrophic prokaryotes that find a wide range of applications in industry due to their broad product spectrum. In this context, the application of cyanobacteria as biofertilizers and thus as an alternative to artificial fertilizers has emerged in recent decades. The benefit is mostly based on the ability of cyanobacteria to fix elemental nitrogen and make it available to the plants in a usable form. However, the positive effects of co-cultivating plants with cyanobacteria are not limited to the provision of nitrogen. Cyanobacteria produce numerous secondary metabolites that can be useful for plants, for example, they can have growth-promoting effects or increase resistance to plant diseases. The effects of biotic and abiotic stress can as well be reduced by many secondary metabolites. Furthermore, the biofilms formed by the cyanobacteria can lead to improved soil conditions, such as increased water retention capacity. To exchange the substances mentioned, cyanobacteria form symbioses with plants, whereby the strength of the symbiosis depends on both partners, and not every plant can form symbiosis with every cyanobacterium. Not only the plants in symbiosis benefit from the cyanobacteria, but also vice versa. This review summarizes the beneficial effects of cyanobacterial co-cultivation on plants, highlighting the substances exchanged and the strength of cyanobacterial symbioses with plants. A detailed explanation of the mechanism of nitrogen fixation in cyanobacterial heterocysts is given. Finally, a summary of possible applications of co-cultivation in the (agrar-)industry is given.
TL;DR: In this paper, the authors showed that G. sulfurreducens was able to fix nitrogen depending on anode respiration, producing a maximum current density of 0.17 ± 0.015 cm−2 and a nitrogen-fixing activity of ca. 0.78μmol C2H4 mg protein−1 h−1, thereby achieving a net total nitrogenfixing rate of 5.6μmg L−1 day−1.
TL;DR: In this paper , a two-dimensional (2D) silicate CaCuSi4O10 nanosheet was prepared by high-temperature solid state method using silica derived from palygorskite clay (Pal) and calcium carbonate derived from egg shells, respectively.
TL;DR: In this paper , the authors showed that G. sulfurreducens was able to fix nitrogen depending on anode respiration, producing a maximum current density of 0.17 ± 0.015 mA cm-2 and a nitrogenfixing activity of ca. 0.78 μmol C2H4 mg protein-1 h-1.
TL;DR: Badila et al. as discussed by the authors determined the existence of novel endophytic diazotrophs through culturable and unculturable bacterial communities (EDBCs) of different tissues (root, stem, and leaf) of five sugarcane cultivars (Saccharum officinarum L. cv.
Abstract: Sugarcane (Saccharum officinarum L.) is one of the world’s highly significant commercial crops. The amounts of synthetic nitrogen (N2) fertilizer required to grow the sugarcane plant at its initial growth stages are higher, which increases the production costs and adverse environmental consequences globally. To combat this issue, sustainable environmental and economic concerns among researchers are necessary. The endophytic diazotrophs can offer significant amounts of nitrogen to crops through the biological nitrogen fixation mediated nif gene. The nifH gene is the most extensively utilized molecular marker in nature for studying N2 fixing microbiomes. The present research intended to determine the existence of novel endophytic diazotrophs through culturable and unculturable bacterial communities (EDBCs). The EDBCs of different tissues (root, stem, and leaf) of five sugarcane cultivars (Saccharum officinarum L. cv. Badila, S. barberi Jesw.cv Pansahi, S. robustum, S. spontaneum, and S. sinense Roxb.cv Uba) were isolated and molecularly characterized to evaluate N2 fixation ability. The diversity of EDBCs was observed based on nifH gene Illumina MiSeq sequencing and a culturable approach. In this study, 319766 operational taxonomic units (OTUs) were identified from 15 samples. The minimum number of OTUs was recorded in leaf tissues of S. robustum and maximum reads in root tissues of S. spontaneum. These data were assessed to ascertain the structure, diversity, abundance, and relationship between the microbial community. A total of 40 bacterial families with 58 genera were detected in different sugarcane species. Bacterial communities exhibited substantially different alpha and beta diversity. In total, 16 out of 20 genera showed potent N2-fixation in sugarcane and other crops. According to principal component analysis (PCA) and hierarchical clustering (Bray–Curtis dis) evaluation of OTUs, bacterial microbiomes associated with root tissues differed significantly from stem and leaf tissues of sugarcane. Significant differences often were observed in EDBCs among the sugarcane tissues. We tracked and validated the plethora of individual phylum strains and assessed their nitrogenase activity with a culture-dependent technique. The current work illustrated the significant and novel results of many uncharted endophytic microbial communities in different tissues of sugarcane species, which provides an experimental system to evaluate the biological nitrogen fixation (BNF) mechanism in sugarcane. The novel endophytic microbial communities with N2-fixation ability play a remarkable and promising role in sustainable agriculture production.
TL;DR: In this article , the authors dealt with the isolation of nitrogen fixing, phosphorus and potassium solubilizing microbes from rhizospheric soil and root's internal tissues of different cereal/pseudocereal crops and their application as a microbial consortium for the growth of cereal crops.
TL;DR: In this paper , the effect of various concentrations of Mo and Fe on photosynthetic and nitrogenase activities under conditions of nitrogen starvation revealed the optimal concentrations of metals that have a stimulating effect on the studied parameters.
Abstract: The potential of cyanobacteria to perform a variety of distinct roles vital for the biosphere, including nutrient cycling and environmental detoxification, drives interest in studying their biodiversity. Increasing soil erosion and the overuse of chemical fertilizers are global problems in developed countries. The option might be to switch to organic farming, which entails largely the use of biofertilisers. Cyanobacteria are prokaryotic, photosynthetic organisms with considerable potential, within agrobiotechnology, to produce biofertilisers. They contribute significantly to plant drought resistance and nitrogen enrichment in the soil. This study sought, isolated, and investigated nitrogen-fixing cyanobacterial strains in rice fields, and evaluated the effect of Mo and Fe on photosynthetic and nitrogenase activities under nitrogen starvation. Cyanobacterial isolates, isolated from rice paddies in Kazakhstan, were identified as Trichormus variabilis K-31 (MZ079356), Cylindrospermum badium J-8 (MZ079357), Nostoc sp. J-14 (MZ079360), Oscillatoria brevis SH-12 (MZ090011), and Tolypothrix tenuis J-1 (MZ079361). The study of the influence of various concentrations of Mo and Fe on photosynthetic and nitrogenase activities under conditions of nitrogen starvation revealed the optimal concentrations of metals that have a stimulating effect on the studied parameters.
TL;DR: A review of the current state of the art of PWBNF can be found in this article , where the authors provide insights into the effective mechanisms for the synthesis of NH3, NO2− and NO3− in highly reactive plasma environments.
Abstract: Nitrogen-based crop fertilizers are the most important industrial chemicals supporting the global food supply. Plasma-water-based nitrogen fixation (PWBNF) provides a clean, sustainable, and flexible alternative, which is amenable for decentralized, small-to-medium-scale production systems. This process is based on the targeted activation of N2 or air molecules by plasmas. Plasma can interact with water molecules, water droplets, and water layers through the plasma physical and chemical mechanisms. This review summarizes the current state of the art of PWBNF and provides insights into the effective mechanisms for the synthesis of NH3, NO2− and NO3− in highly reactive plasma environments. The opportunities and challenges for this plasma-enabled approach are identified to guide the development of sustainable nitrogen fixation technology.
TL;DR: In this article , the authors show that nitrate transport via NITRATE TRANSPORTER 2.1 (LjNRT2.1) is a key step in the NLP signaling pathway to control nodulation.
Abstract: Legumes have adaptive mechanisms that regulate nodulation in response to the amount of nitrogen in the soil. In Lotus japonicus, two NODULE INCEPTION (NIN)-LIKE PROTEIN (NLP) transcription factors, LjNLP4 and LjNLP1, play pivotal roles in the negative regulation of nodulation by controlling the expression of symbiotic genes in high nitrate conditions. Despite an improved understanding of the molecular basis for regulating nodulation, how nitrate plays a role in the signaling pathway to negatively regulate this process is largely unknown. Here, we show that nitrate transport via NITRATE TRANSPORTER 2.1 (LjNRT2.1) is a key step in the NLP signaling pathway to control nodulation. A mutation in the LjNRT2.1 gene attenuates the nitrate-induced control of nodulation. LjNLP1 is necessary and sufficient to induce LjNRT2.1 expression, thereby regulating nitrate uptake/transport. Our data suggest that LjNRT2.1-mediated nitrate uptake/transport is required for LjNLP4 nuclear localization and induction/repression of symbiotic genes. We further show that LjNIN, a positive regulator of nodulation, counteracts the LjNLP1-dependent induction of LjNRT2.1 expression, which is linked to a reduction in nitrate uptake. These findings suggest a plant strategy in which nitrogen acquisition switches from obtaining nitrogen from the soil to symbiotic nitrogen fixation.
TL;DR: In this article , the authors theoretically predict the electronic structure of FeMo(Se, Te) composed of tri-coordinated Fe species with open shells for binding with Se, which forms a collective electron pool for promoting N 2 activation.
Abstract: It has been long believed that FeMoS structure, where Fe is bonded with S, plays a pivotal role as a biomimetic catalyst for electrochemical nitrogen (N 2 ) fixation . Nevertheless, the structure of Fe bonded to heavier analogues (Se or Te) has never been explored for N 2 electrofixation. Here, we theoretically predict the electronic structure of FeMo(Se, Te) composed of tri-coordinated Fe species with open shells for binding with Se, which forms a collective electron pool for promoting N 2 activation. Guided by this interesting prediction, we then demonstrate a two-step procedure to synthesize such structures, which displays remarkable N 2 electrofixation activities with ammonia yield of 72.54 μg h -1 mg -1 and Faradic efficiency of 51.67% that are more than three times of the FeMoS counterpart. Further mechanism study has been conducted through density function theory (DFT) simulations. This work would provide new clues for designing versatile electrocatalytic materials for large-scale industrialization.