Role In Nitrogen Fixation Research Articles

Influence of Growth Support on the Diversity, Composition, and Functionality of Microbial Communities Associated with Tillandsia recurvata

Tillandsia recurvata is an epiphytic plant commonly found in tropical regions and colonizes tree trunks, fences, and power wires. This plant plays an important role in interacting with trees, sharing microorganisms, and performing specific functions in the process of tree colonization. The objective of this study was to evaluate and compare the microbiomes of T. recurvata collected from two different locations (trees and fences) and two plant tissues (leaves and roots). The hypothesis of this study was that the microbiome of T. recurvata is composed of microorganisms that would provide nutritional support to compensate for the lack of nutrients in a particular growth support. The results showed significant differences in microbial diversity between trees and fences, with trees exhibiting higher richness and more complex microbial networks. Proteobacteria was the most prevalent bacterial phylum, with Actinobacteria and Sphingomonas also playing key roles in nitrogen fixation and plant growth. Fungal communities were similar across locations, with Ascomycota and Basidiomycota being predominant, but Paraconiothyrium and Nigrospora showed significant differences in abundance between trees and fences. Functional analysis indicated similar metabolic profiles across leaf and root samples, with key functions for T. recurvata including carbohydrate and amino acid metabolism, stress control, and biofertilization.

Seasonal Dynamics of Trichodesmium and Phytoplankton Communities in the Eastern Arabian Sea: Winter Vs Spring-inter monsoon

The filamentous marine cyanobacterium Trichodesmium forms extensive blooms in tropical seas, where it plays an important role in nitrogen fixation. This study investigated Trichodesmium-associated phytoplankton in the Eastern Arabian Sea (EAS) during bloom and nonbloom conditions. Trichodesmium blooms over the continental shelf primarily comprised of T. erythraeum and T. thiebautii during the Spring Inter Monsoon (SIM) and T. erythraeum during the Winter Monsoon (WM). T. erythreaum blooms have rarely been reported from the north-east Arabian Sea during WM. Trichomes comprised of 143-1552 cells during the WM, with filaments ranging from 1339 to 13163 µm in length. Non-diazotrophic groups like diatoms and dinoflagellates were associated with Trichodesmium during both seasons within the bloom waters. The study found a novel symbiotic relationship between the heterocystous diazotroph Richelia intracellularis and Nitzschia sicula during WM blooms. This research expands knowledge of lesser-known phytoplankton species and their associations in the EAS.

Plant Growth Promoting Rhizobacteria Bio Capsules: Enhancing Ginger Growth and Yield

The study aimed to assess the impact of plant growth promoting rhizobacteria capsules on the growth and yield of ginger. PGPRs known for their role in nitrogen fixation, phosphate solubilization, and hormone secretion. These PGPR’s tested at the Turmeric Research Station, Kammarpally across three consecutive years (2018-2021) in combination with three ginger varieties (Mahima, Maran, Local type) and five different treatments T1-POP + Trichoderma (Talc formulations) + GRB 35 (Talc formulations), T2- POP + Trichoderma capsules + GRB 35 capsule, T3- POP + Trichoderma capsules, T4- POP + GRB 35 capsule, T5- POP (Recommended package of practices). The treatment T4V1 (POP + GRB 35 capsule with Mahima variety), produced the highest fresh rhizome yield with 6.28 kg plot-1 and 21.53 t ha-1 followed by T4V2 (POP + GRB 35 capsule with Maran variety) at 6.16 kg plot-1 and 20.15 t ha-1. These results suggest that GRB 35 capsules significantly enhance ginger yield, offering a sustainable approach to ginger cultivation.

Phytobiomes: Harnessing the Power of Microbial Communities for Plant Health

Phytobiomes encompass the dynamic ecosystems surrounding plants, which include a diverse range of microbial communities such as fungi, bacteria, algae, viruses, and nematodes. These microorganisms interact intricately with plants, influencing their health, growth, and resilience. Beneficial fungi form symbiotic relationships with plant roots, enhancing nutrient absorption, while bacteria play a role in nitrogen fixation and disease suppression. Algae contribute to soil health and organic matter decomposition, and viruses, though often seen as harmful, can provide resistance to certain pathogens. Nematodes, both beneficial and parasitic, regulate soil nutrient cycles and influence plant growth. Harnessing the potential of these microbial communities offers promising solutions for sustainable agriculture. By promoting beneficial interactions within the phytobiome, it is possible to improve plant productivity, enhance nutrient use efficiency, and increase tolerance to environmental stresses such as drought, salinity, and pathogens. Phytobiome research aims to uncover the complex relationships within these microbial networks to develop novel agricultural practices that reduce reliance on chemical inputs. This holistic approach not only promotes plant health but also ensures ecological balance, contributing to the long-term sustainability of agroecosystems in the face of environmental challenges. Understanding the power of microbial communities within phytobiomes is key to advancing future agricultural innovations.

An Efficient and Low-Cost Deep Learning-Based Method for Counting and Sizing Soybean Nodules

Soybeans are an essential source of food, protein, and oil worldwide, and the nodules on their root systems play a critical role in nitrogen fixation and plant growth. In this study, we tackled the challenge of limited high-resolution image quantities and the constraints on model learning by innovatively employing image segmentation technology for an in-depth analysis of soybean nodule phenomics. Through a meticulously designed segmentation algorithm, we broke down large-resolution images into numerous smaller ones, effectively improving the model’s learning efficiency and significantly increasing the available data volume, thus laying a solid foundation for subsequent analysis. In terms of model selection and optimization, after several rounds of comparison and testing, YOLOX was identified as the optimal model, achieving an accuracy of 91.38% on the test set with an R2 of up to 86%, fully demonstrating its efficiency and reliability in nodule counting tasks. Subsequently, we utilized YOLOV5 for instance segmentation, achieving a precision of 93.8% in quickly and accurately extracting key phenotypic indicators such as the area, circumference, length, and width of the nodules, and calculated the statistical properties of these indicators. This provided a wealth of quantitative data for the morphological study of soybean nodules. The research not only enhanced the efficiency and accuracy of obtaining nodule phenotypic data and reduced costs but also provided important scientific evidence for the selection and breeding of soybean materials, highlighting its potential application value in agricultural research and practical production.

Isolation and Characterization of Plant Growth Promoting Bacteria from Contaminated Soil and their Impact on Triticum Aestivum

Plant growth promoting bacteria (PGPB) or plant growth promoting rhizobacteria (PGPR) are bacteria that exist in the rhizospheres of plant soil and form symbiotic relationships with the plant.Some of the methods through which PGPR aid in plant growth is by playing a role in nitrogen fixation, phosphate solubilization, iron chelation, reduction of heavy metal uptake by plant, reducing spread of plant diseases, secretion of phytohormones, significantly influencing root morphology and growth and by increasing the bio-availability of nutrients in the soil. One way to develop methods to cultivate this crop by using sustainable methods that can also increase the quality and yield of this crop is by treating the seeds of this plant with PGPB. In this study we examined the potential impact of bacteria, isolated from contaminated soil, on plant development and growth promotion. Our study aimed to isolate and characterize these bacteria and, after treatment of the seeds of Triticum aestivum with each of the bacterial isolates, test their ability to positively influence the growth of Triticum aestivum. After isolation and purification of the bacterial strains via quadrant streaking, we performed microscopic analysis and biochemical tests on the bacterial isolates which were thus identified to be Escherichia coli, Staphylococcus aureus and Pseudomonas spp. We compared the growth of the seeds treated with each bacterial isolate with that of the control. The parameters that were taken into account and compared were root and stem length and the number of leaves, branches and roots. E.coli increased the steam and root length of wheat whereas, S.aureus increased the number of branches but it decreased the root length. While Pseudomonas spp. increased the stem and root length and increased the number of branches. Hence, Pseudomonas spp. was the most effective boosting more aspects of wheat growth in comparison to E.coli and S.aureus.

Two distinct ferredoxins are essential for nitrogen fixation by the iron nitrogenase in Rhodobacter capsulatus.

Nitrogenases are the only enzymes able to fix gaseous nitrogen into bioavailable ammonia and hence are essential for sustaining life. Catalysis by nitrogenases requires both a large amount of ATP and electrons donated by strongly reducing ferredoxins or flavodoxins. Our knowledge about the mechanisms of electron transfer to nitrogenase enzymes is limited: The electron transport to the iron (Fe)-nitrogenase has hardly been investigated. Here, we characterized the electron transfer pathway to the Fe-nitrogenase in Rhodobacter capsulatus via proteome analyses, genetic deletions, complementation studies, and phylogenetics. Proteome analyses revealed an upregulation of four ferredoxins under nitrogen-fixing conditions reliant on the Fe-nitrogenase in a molybdenum nitrogenase knockout strain, compared to non-nitrogen-fixing conditions. Based on these findings, R. capsulatus strains with deletions of ferredoxin (fdx) and flavodoxin (fld, nifF) genes were constructed to investigate their roles in nitrogen fixation by the Fe-nitrogenase. R. capsulatus deletion strains were characterized by monitoring diazotrophic growth and Fe-nitrogenase activity in vivo. Only deletions of fdxC or fdxN resulted in slower growth and reduced Fe-nitrogenase activity, whereas the double deletion of both fdxC and fdxN abolished diazotrophic growth. Differences in the proteomes of ∆fdxC and ∆fdxN strains, in conjunction with differing plasmid complementation behaviors of fdxC and fdxN, indicate that the two Fds likely possess different roles and functions. These findings will guide future engineering of the electron transport systems to nitrogenase enzymes, with the aim of increased electron flux and product formation.IMPORTANCENitrogenases are essential for biological nitrogen fixation, converting atmospheric nitrogen gas to bioavailable ammonia. The production of ammonia by diazotrophic organisms, harboring nitrogenases, is essential for sustaining plant growth. Hence, there is a large scientific interest in understanding the cellular mechanisms for nitrogen fixation via nitrogenases. Nitrogenases rely on highly reduced electrons to power catalysis, although we lack knowledge as to which proteins shuttle the electrons to nitrogenases within cells. Here, we characterized the electron transport to the iron (Fe)-nitrogenase in the model diazotroph Rhodobacter capsulatus, showing that two distinct ferredoxins are very important for nitrogen fixation despite having different redox centers. In addition, our research expands upon the debate on whether ferredoxins have functional redundancy or perform distinct roles within cells. Here, we observe that both essential ferredoxins likely have distinct roles based on differential proteome shifts of deletion strains and different complementation behaviors.

Simultaneous remediation of diesel-polluted soil and promoted ryegrass growth by non-thermal plasma pretreatment

The remediation of petroleum-polluted soil has garnered significant global attention. In this study, a pot-culture experiment was conducted to assess the feasibility of using non-thermal plasma (NTP) as an efficient and economic-friendly pretreatment method in the phytoremediation of diesel-polluted soil. The remediation effectiveness was evaluated via both the removal of diesel and the ryegrass growth. Specifically, at the 50th d of ryegrass growth, the increase of diesel removal efficiency with NTP pretreatment ranged from 16 % to 30 %. Moreover, both clean and diesel-polluted soils pretreated by NTP promoted the growth of ryegrass in shoot lengths and biomass especially after the 35th d. It was found that nitrate nitrogen fixed by NTP not only stimulated the nitrate reductase activities in leaves and promoted plant growth, but also was transformed to more ammonia nitrogen for organism life activity. Subsequent investigation proved that the related nitrogen-metabolism activities of microbes were enriched in rhizosphere soils with NTP pretreatment. Furthermore, NTP treatment increased the abundance of beneficial microbial communities in diesel soil rhizosphere on the 42nd d of growth period. In addition, changes in the proportions of soil dissolved organic matter indicated enhanced nutrient cycling in soils with NTP pretreatment. These promotional effects underscored the contribution of NTP pretreatment in rapidly detoxifying diesel-contaminated soil within 10 min and accelerated the establishment of ryegrass ecosystem. This study provides valuable insights into the role of nitrogen fixation and offers an efficient and promising advanced approach for the phytoremediation of diesel-polluted soil with NTP pretreatment.

Nodule-specific Cu+ -chaperone NCC1 is required for symbiotic nitrogen fixation in Medicago truncatula root nodules.

Cu+ -chaperones are a diverse group of proteins that allocate Cu+ ions to specific copper proteins, creating different copper pools targeted to specific physiological processes. Symbiotic nitrogen fixation carried out in legume root nodules indirectly requires relatively large amounts of copper, for example for energy delivery via respiration, for which targeted copper deliver systems would be required. MtNCC1 is a nodule-specific Cu+ -chaperone encoded in the Medicago truncatula genome, with a N-terminus Atx1-like domain that can bind Cu+ with picomolar affinities. MtNCC1 is able to interact with nodule-specific Cu+ -importer MtCOPT1. MtNCC1 is expressed primarily from the late infection zone to the early fixation zone and is located in the cytosol, associated with plasma and symbiosome membranes, and within nuclei. Consistent with its key role in nitrogen fixation, ncc1 mutants have a severe reduction in nitrogenase activity and a 50% reduction in copper-dependent cytochrome c oxidase activity. A subset of the copper proteome is also affected in the ncc1 mutant nodules. Many of these proteins can be pulled down when using a Cu+ -loaded N-terminal MtNCC1 moiety as a bait, indicating a role in nodule copper homeostasis and in copper-dependent physiological processes. Overall, these data suggest a pleiotropic role of MtNCC1 in copper delivery for symbiotic nitrogen fixation.

Exploring microbial degradation of polyamide 4 in soils: Unveiling degradation mechanisms, pathways, and the contribution of strain NR4

Evidence for microbial degradation of polyamide 4 (PA4) has previously been reported, but little is available on the specific strains and enzymes. The mechanism responsible for the degradation is still unknown. This study investigated the degradation behaviors of PA4 films in composted, garbage and campus soil. Various characterization methods were used to evaluate the changes in morphology, structure, crystallinity, and thermal properties of PA4 films during the soil biodegradation, to assess its degradation efficiency in four types of soils. The results showed that the highest degradation behavior of soil in composted soil that almost no residual films can be observed in this type of soil after 60 days, compared to those in garbage and campus soil. PA4 degradation resulting occurring in soils can enhance the population of certain beneficial microorganisms in the soil environment, such as Ensifer, Luteimonas, etc., which play a key role in nitrogen fixation, promoting plant growth, and carbon cycling. Moreover, a highly efficient single bacterium for PA4 degradation was isolated from the soil enriched and acclimated by PA4 films, named strain NR4. The complete genome of strain NR4 was sequenced to identify relevant enzyme-coding genes and metabolic pathways associated with PA4 degradation, ultimately leading to the proposal of a mechanism for PA4 biodegradation. The research not only examined how PA4 degrades in different types of soil but also suggested practical recommendations for promoting biodegradation of other products in the nylon family. The results obtained from the current study are essential in addressing environmental issues surrounding the buildup of non-biodegradable nylon items in the ecosystem.

Unusual Hydrogenation Reactivities of a Thiolate-Bridged Dicobalt μ-Nitride Featuring a Bent {CoIII-N-CoIII} Core.

Transition metal nitrides have received considerable attention owing to their crucial roles in nitrogen fixation and nitrogen atom transfer reactions. Compared to the early and middle transition metals, it is much more challenging to access late transition metal nitrides, especially cobalt in group 9. So far, only a handful of cobalt nitrides have been reported; consequently, their hydrogenation reactivity is largely unexplored. Herein, we present a structurally and spectroscopically well-characterized thiolate-bridged dicobalt μ-nitride [Cp*CoIII(μ-SAd)(μ-N)CoIIICp*] (2) featuring a bent {CoIII(μ-N)CoIII} core. Remarkably, complex 2 can realize not only direct hydrogenation of nitride to amide but also stepwise N-H bond formation from nitride to ammonia. Specifically, 2 can facilely activate dihydrogen (H2) at mild conditions to generate a dicobalt μ-amide [Cp*CoII(μ-SAd)(μ-NH2)CoIICp*] (4) via an unusual mechanism of two-electron oxidation of H2 as proposed by computational studies; in the presence of protons (H+) and electrons, nitride 2 can convert to dicobalt μ-imide [Cp*CoIII(μ-SAd)(μ-NH)CoIIICp*][BPh4] (3[BPh4]) and to CoIICoII μ-amide 4, and finally release ammonia. In contrast to 2, the only other structurally characterized dicobalt μ-nitride Na(THF)4{[(ketguan)CoIII(N3)]2(μ-N)} (ketguan = [(tBu2CN)C(NDipp)2]-, Dipp = 2,6-diisopropylphenyl) (e) that possesses a linear {CoIII(μ-N)CoIII} moiety cannot directly react with H2 or H+. Further in-depth electronic structure analyses shed light on how the varying geometries of the {CoIII(μ-N)CoIII} moieties in 2 and e, bent vs linear, impart their disparate reactivities.

Effect of Co-Application of Azospirillum brasilense and Rhizobium pisi on Wheat Performance and Soil Nutrient Status under Deficit and Partial Root Drying Stress.

Water management techniques are improving at the farm level, but they are not enough to deal with the limited availability of water and increased crop yields. Soil microbes play a vital role in nitrogen fixation, improving soil fertility and enhancing plant growth hormones under drought conditions. Therefore, this study was conducted to investigate the impact of water management combined with Azospirillum brasilense and Rhizobium pisi on wheat crop productivity and soil properties in dry regions. Three water management techniques were compared, normal irrigation as a control (C), deficit irrigation (DI), and partial root drying irrigation (PRD), together with the interaction of plant-growth-promoting rhizobacteria (PGPR). Experiments were conducted with six treatments in total: T1 = C + No PGPR, T2 = C + PGPR, T3 = DI + No PGPR, T4 = DI + PGPR, T5 = PRD + No PGPR, and T6 = PRD + PGPR. The highest grain yield was achieved in the control irrigation treatment using seeds inoculated with rhizobacteria, followed by control treatment without any inoculation, and the lowest was recorded with deficit irrigation without rhizobacteria inoculated in the seeds. However, PRD irrigation resulted in significantly higher plant growth and grain yield than the DI treatment. PGPR inoculation combined with PRD resulted in a 22% and 20% higher number of grains per spike, a 19% and 21% higher grain yield, and a 25% and 22% higher crop growth rate compared to rhizobacteria inoculation combined with the DI system in 2021-22 and 2022-23, respectively. This increase was due to the higher production of growth hormones and higher leaf area index under water-limited conditions. A greater leaf area index leads to a higher chlorophyll content and higher food production for plant growth.

Expanding the FurC (PerR) regulon in Anabaena (Nostoc) sp. PCC 7120: Genome-wide identification of novel direct targets uncovers FurC participation in central carbon metabolism regulation.

FurC (PerR, Peroxide Response Regulator) from Anabaena sp. PCC 7120 (also known as Nostoc sp. PCC 7120) is a master regulator engaged in the modulation of relevant processes including the response to oxidative stress, photosynthesis and nitrogen fixation. Previous differential gene expression analysis of a furC-overexpressing strain (EB2770FurC) allowed the inference of a putative FurC DNA-binding consensus sequence. In the present work, more data concerning the regulon of the FurC protein were obtained through the searching of the putative FurC-box in the whole Anabaena sp. PCC 7120 genome. The total amount of novel FurC-DNA binding sites found in the promoter regions of genes with known function was validated by electrophoretic mobility shift assays (EMSA) identifying 22 new FurC targets. Some of these identified targets display relevant roles in nitrogen fixation (hetR and hgdC) and carbon assimilation processes (cmpR, glgP1 and opcA), suggesting that FurC could be an additional player for the harmonization of carbon and nitrogen metabolisms. Moreover, differential gene expression of a selection of newly identified FurC targets was measured by Real Time RT-PCR in the furC-overexpressing strain (EB2770FurC) comparing to Anabaena sp. PCC 7120 revealing that in most of these cases FurC could act as a transcriptional activator.

Single-cell RNA-seq of Lotus japonicus provide insights into identification and function of root cell types of legume.

The roots of legume plant play a crucial role in nitrogen fixation. However, the transcriptomes of different cell types of legume root and their functions remain largely unknown. Here, we performed single-cell RNA sequencing and profiled more than 22,000 single cells from root tips of Lotus japonicus, a model species of legume. We identified seven clusters corresponding to seven major cell types, which were validated by in situ hybridization. Further analysis revealed regulatory programs including phytohormone and nodulation associated with specific cell types, and revealed conserved and diverged features for the cell types. Our results represent the first single-cell resolution transcriptome for legume root tips and a valuable resource for studying the developmental and physiological functions of various cell types in legumes.

The role of nitrogen fixation and crop N dynamics on performance and legacy effects of maize-grain legumes intercrops on smallholder farms in Tanzania

Maize-grain legume intercrops form an important component of the cropping systems of smallholder farmers in many parts of sub-Saharan Africa. However, the effects of cropping system and fertilizer use on nitrogen fixation and nitrogen uptake of component crops in maize-legume intercrops are not well understood. Our study addressed the questions: (i) What is the capacity of pigeonpea and lablab to fix atmospheric nitrogen (N2) in sole crop and when intercropped with maize on smallholder farms across different agro-ecological conditions?; (ii) How does productivity and N-uptake by sole and intercropped maize and legumes respond to N and P fertilizer?; and (iii) What are the residual effects of the sole crops, intercrops and fertilizer treatments on the productivity of a succeeding maize crop? We studied additive intercropping systems on eight farms in Babati, Tanzania: maize-long duration pigeonpea, maize-medium duration pigeonpea and maize-lablab, with separate sole crops, at three fertilizer rates: no fertilizer; 40 kg P ha−1; and 90 kg N ha−1 + 40 kg P ha−1. Whereas P fertilizer was applied on maize and the legumes, the N fertilizer was only applied on maize. Maize and pigeonpea were sown simultaneously, while lablab was relay-planted one month later. N2-fixation was quantified using the 15N natural abundance method. N2-fixation differed among the legume species. Sole long-duration pigeonpea fixed significantly more N2 (20–63 kg ha−1 more) than all other cropping systems, corresponding to the greater shoot dry matter and N yield of this system. The combined N uptake of maize and legume in intercrops was consistently larger than that of sole maize or the legume. Application of fertilizer resulted in enhanced N uptake both in the current season (up to 40 kg N ha−1 more) and in a succeeding maize crop (up to 71 kg N ha−1 more). We observed positive associations between grain yield, dry matter production and total N uptake of a succeeding maize crop, and the N-fixed by legume species in the preceding season. Each kg of legume shoot N yield was associated with up to 14 kg ha−1 extra grain yield, 29 kg ha−1 extra dry matter and 0.5 kg ha−1 extra total N uptake of the succeeding maize crop. Our results show that maize-legume intercrops enhance N-uptake. Furthermore, N2-fixation by sole or intercropped legumes confers strong residual benefits on productivity of a succeeding maize crop.

Multifunctional attributes of endophytic Pseudomonas strains isolated from the leaves of medicinal plants

Endophytic bacteria are responsible for improved plant growth due to its role in nitrogen fixation, indole acetic acid (IAA) production, phosphate solubilization etc and in plant protection through various mechanisms and production of bioactive compounds. The purpose of this study was to determine the plant growth promoting potential of endophytic bacteria isolated from medicinal plants namely, Adulsa, Amla, Bael, Kadamb, Mango, Neem, Tulsi. Endophytic bacteria isolated from the medicinal plants, comprised of 68% Gram positive and 29% Gram negative bacteria. Seventeen distinctly unique Gram-negative endophytes were selected for further analysis. The selected endophytes were tentatively identified as Pseudomonas sp. The multifarious endophytes were capable of nitrogen fixation, phosphate solubilisation, indole acetic acid (IAA) production, production of antimicrobial compounds and aromatic compound degradation. Some of the endophytic strains were found to harbor plasmids that may play a role in aromatic compound degradation. This study emphasizes the potential of endophytic Pseudomonas species in enhancing plant growth and plant protection.

Mechanism associated with the positive effect of nanocellulose on nitrogen retention in a manure composting system

Additives can play important roles in effectively inhibiting nitrogen losses during livestock manure composting due to the activities of microbes. This study investigated the effects of adding nanocellulose at 300 mg/kg, 600 mg/kg, and 900 mg/kg (NC900) on nitrogen conversion, nitrogen conversion functional genes, and related microorganisms during composting. The results showed that compared with the control, nanocellulose hindered the ammoniation reaction. In addition, NC900 promoted nitrification, interfered with the denitrification process, and reduced the abundance of the nirK gene, thereby increasing the nitrate nitrogen content and decreasing ammonia spillover. NC900 promoted nitrogen fixation by increasing the abundance of members of Rhizobiales, which play important roles in nitrogen fixation. In general, compared with the control, NC900 improved the retention of nitrogen by controlling ammonia emissions. The results obtained in this study demonstrate that nanocellulose can be applied in the treatment of organic solid waste and agricultural production.

The Relation Ship Between Total Soil Microbes With N, P , K Nutrient Levels By Paddy Plant (Case Study In Ajamu Village, Panai Hulu District, Labuhanbatu Regency)

The neglect of returning organic matter to the soil and the intensive use of chemical fertilizers inpaddy fields have caused the physical, chemical, and biological quality of the soil to decline. Such soilconditions cause the population of soil biota that plays a role in nitrogen fixation and phosphatesolubility to decrease. This study aims to determine the relationship between total microbes andnutrient levels of N, P, K in rice plants in Ajamu Village, Panai Hulu District, Labuhan Batu Regency.This research was conducted from December 2021 to January 2022. Sampling was carried out bytaking leaves and rhizosphere soil of rice plants at 5 zigzag sampling points in a rice field area.Parameters observed in this study were nutrient levels of N, P, K and total microbes. The analysis wascarried out using correlation and regression methods.

Effect of thermophilic microbial agents on nitrogen transformation, nitrogen functional genes, and bacterial communities during bean dregs composting.

This study explored how a thermophilic microbial agent altered nitrogen transformation, nitrogen functional genes, and bacterial communities during bean dregs composting with (T) and without (CK) a thermophilic microbial agent for 15days. The results showed that the maximum temperature in T reached 73°C and remained above 70°C for 8days, while that in CK was only 65°C. The pH in T had essentially stabilized on day 7, while that in CK was still increasing. On day 15, the seed germination index (GI) of T (95%) reached maturity (defined by GI ≥ 85%), while the GI of CK was only 36%. The concentrations of total nitrogen, water-soluble nitrogen, ammonia nitrogen, and nitrate nitrogen in T (2.5%, 18.9g/kg, 8.75g/kg, and 1.69g/kg) were all lower than those in CK (3.6%, 28.9g/kg, 12.75g/kg, and 6.82g/kg). During composting, Bacillus played a major role in nitrogen reduction, nitrogen mineralization, denitrification, and the conversion between nitrite and nitrate. Weissella played a major role in nitrogen assimilation. Komagataeibacter and Bacillus played a major role in nitrogen fixation in CK and T, respectively. Nitrification was not observed during composting. The nosZ gene, which converts nitrous oxide to nitrogen, was found only in T. Network analysis suggested that the average number of neighbours in T was 3.30% higher than that in CK and the characteristic path length in T was 14.15% higher than that in CK. Therefore, the thermophilic microbial agents could cause nitrogen loss but promote the maturity of bean dregs, which have great potential application.

A comparative study on the reactivity of ditantalum deuteride cluster anions Ta2D2- and Ta2D4- toward N2.

The activation and transformation of molecular nitrogen (N2) by metal hydride species has attracted widespread attention due to its critical role in nitrogen fixation. Herein, the reactions between tantalum deuteride cluster anions Ta2D2,4- and N2 were investigated experimentally and theoretically. An unprecedented reaction channel of the liberation of a single D atom was observed and much superior reactivity was identified for Ta2D4-. Theoretical investigations indicate that the releasing of D atoms benefits from the completely dissociative adsorption of N2 on the dinuclear metal centres. The extra D atoms in Ta2D4- compared to Ta2D2- are helpful to create sufficient electron density at the adsorption site and modify the symmetry of active orbitals to facilitate a further reduction of N2. This comparative study provides a molecular-level insight to understand the high structure-modulating capability of the additional hydride ligands in polyhydride species in the adsorption and activation of nitrogen molecules.