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The Science of the Total Environment Mar 2024Biological nitrogen fixation (BNF) is strongly affected by the carbon (C) and nitrogen (N) stoichiometry in soil and depends on the input of organic C. Due to the high...
Biological nitrogen fixation (BNF) is strongly affected by the carbon (C) and nitrogen (N) stoichiometry in soil and depends on the input of organic C. Due to the high metabolic costs of nitrogenase activity, however, the response of BNF to organic C input and its impact on microbial turnover remain unclear. To address this knowledge gap, we combined N tracing with high-throughput sequencing by adding glucose or glucose plus mineral N fertilizer for a 12-day incubation in three cropland soils. Glucose addition alone strongly changed the BNF activity (0.76-2.51 mg N kg d), while BNF was completely absent after mineral N fertilization. This switch-on of BNF by glucose addition supported equally high rates of microbial growth and organic C mineralization compared with the direct mineral N assimilation by microorganisms. Glucose-induced BNF was predominantly catalyzed by Azotobacter-affiliated free-living diazotrophs (>50 % of the total nifH genes), which increased with diverse nondiazotrophs such as Nitrososphaera, Bacillus and Pseudoxanthomonas. Structural equation models (SEMs) and random forest (RF) analyses consistently revealed that the soil C:N ratio and Azotobacter-affiliated diazotrophic abundances were the key factors affecting glucose-induced BNF. Our findings emphasize the importance of free-living diazotrophs for microbial turnover of organic C in soil.
Topics: Nitrogen Fixation; Soil; Nitrogen; Minerals; Glucose; Crops, Agricultural; Soil Microbiology
PubMed: 38220009
DOI: 10.1016/j.scitotenv.2024.170081 -
Journal of Inorganic Biochemistry Apr 2024The light-driven reduction of dinitrogen (N) to ammonia (NH) catalyzed by a cadmium sulfide (CdS) nanocrystal‑nitrogenase MoFe protein biohybrid is dependent on a...
The light-driven reduction of dinitrogen (N) to ammonia (NH) catalyzed by a cadmium sulfide (CdS) nanocrystal‑nitrogenase MoFe protein biohybrid is dependent on a range of different factors, including an appropriate hole-scavenging sacrificial electron donor (SED). Here, the impact of different SEDs on the overall rate of N reduction catalyzed by a CdS quantum dot (QD)-MoFe protein system was determined. The selection of SED was guided by several goals: (i) molecules with standard reduction potentials sufficient to reduce the oxidized CdS QD, (ii) molecules that do not absorb the excitation wavelength of the CdS QD, and (iii) molecules that could be readily reduced by sustainable processes. Earlier studies utilized buffer molecules or ascorbic acid as the SED. The effectiveness of ascorbic acid as SED was compared to dithionite (DT), triethanolamine (TEOA), and hydroquinone (HQ) across a range of concentrations in supporting N reduction to NH in a CdS QD-MoFe protein photocatalytic system. It was found that TEOA supported N reduction rates comparable to those observed for dithionite and ascorbic acid. HQ was found to support significantly higher rates of N reduction compared to the other SEDs at a concentration of 50 mM. A comparison of the rates of N reduction by the biohybrid complex to the standard reduction potential (E) of the SEDs reveals that E is not the only factor impacting the efficiency of hole-scavenging. These findings reveal the importance of the SED properties for improving the efficiency of hole-scavenging in the light-driven N reduction reaction catalyzed by a CdS QD-MoFe protein hybrid.
Topics: Nitrogenase; Molybdoferredoxin; Oxidation-Reduction; Dithionite; Catalysis; Ascorbic Acid; Azotobacter vinelandii; Sulfides; Cadmium Compounds
PubMed: 38219407
DOI: 10.1016/j.jinorgbio.2024.112484 -
Plants (Basel, Switzerland) Dec 2023The amalgamation of mineral and targeted bacterial preparations represents a new generation of agricultural technology. Inoculation with combined preparations of...
The amalgamation of mineral and targeted bacterial preparations represents a new generation of agricultural technology. Inoculation with combined preparations of microorganisms is more effective than inoculation with a single microorganism in stimulating plant growth by providing a more balanced diet for various crops. In this work, the effect of inoculation of 20 consortium variants on the yield indicators of three crops (wheat, buckwheat, corn) and the soil microbiome in the open field was investigated. The soil microbiome was defined by 16S rRNA sequences through NGS. The species richness of the soil microbial community (alpha diversity) was similar for all studied samples. A beta-diversity analysis revealed that the microbial diversity of three soil samples (C.bw, F.bw and Soil.bw) differed significantly from all others. At the phylum level, the number of and in these samples was increased. For the combination "Consortium C ( and )-buckwheat", a systemic positive improvement in all growth and yield indicators was observed. The soil of the site where buckwheat grew, inoculated by Consortium C, contained significantly more available phosphorus than all other soil samples. Such results can be explained both by the direct action of a consortium of phosphate-immobilizing and nitrogen-fixing bacteria and acidification of the medium due to an increase in phylum bacteria in the soil.
PubMed: 38202424
DOI: 10.3390/plants13010116 -
MBio Feb 2024Biological nitrogen fixation, the conversion of inert N to metabolically tractable NH, is only performed by certain microorganisms called diazotrophs and is catalyzed by...
Biological nitrogen fixation, the conversion of inert N to metabolically tractable NH, is only performed by certain microorganisms called diazotrophs and is catalyzed by the nitrogenases. A [7Fe-9S-C-Mo--homocitrate]-cofactor, designated FeMo-co, provides the catalytic site for N reduction in the Mo-dependent nitrogenase. Thus, achieving FeMo-co formation in model eukaryotic organisms, such as , represents an important milestone toward endowing them with a capacity for Mo-dependent biological nitrogen fixation. A central player in FeMo-co assembly is the scaffold protein NifEN upon which processing of NifB-co, an [8Fe-9S-C] precursor produced by NifB, occurs. Prior work established that NifB-co can be produced in mitochondria. In the present work, a library of genes from diverse diazotrophs was expressed in , targeted to mitochondria, and surveyed for their ability to produce soluble NifEN protein complexes. Many such NifEN variants supported FeMo-co formation when heterologously produced in the diazotroph . However, only three of them accumulated in soluble forms in mitochondria of aerobically cultured . Of these, two variants were active in the FeMo-co synthesis assay. NifEN, NifB, and NifH proteins from different species, all of them produced in and purified from mitochondria, were combined to establish successful FeMo-co biosynthetic pathways. These findings demonstrate that combining diverse interspecies nitrogenase FeMo-co assembly components could be an effective and, perhaps, the only approach to achieve and optimize nitrogen fixation in a eukaryotic organism.IMPORTANCEBiological nitrogen fixation, the conversion of inert N2 to metabolically usable NH3, is a process exclusive to diazotrophic microorganisms and relies on the activity of nitrogenases. The assembly of the nitrogenase [7Fe-9S-C-Mo--homocitrate]-cofactor (FeMo-co) in a eukaryotic cell is a pivotal milestone that will pave the way to engineer cereals with nitrogen fixing capabilities and therefore independent of nitrogen fertilizers. In this study, we identified NifEN protein complexes that were functional in the model eukaryotic organism . NifEN is an essential component of the FeMo-co biosynthesis pathway. Furthermore, the FeMo-co biosynthetic pathway was recapitulated using only proteins expressed in . FeMo-co biosynthesis was achieved by combining nitrogenase FeMo-co assembly components from different species, a promising strategy to engineer nitrogen fixation in eukaryotic organisms.
Topics: Nitrogenase; Saccharomyces cerevisiae; Molybdoferredoxin; Bacterial Proteins; Mitochondria; Nitrogen; Tricarboxylic Acids; Iron Compounds
PubMed: 38126768
DOI: 10.1128/mbio.03088-23 -
Frontiers in Plant Science 2023Microbial-based biostimulants, functioning as biotic and abiotic stress protectants and growth enhancers, are becoming increasingly important in agriculture also in the...
Microbial-based biostimulants, functioning as biotic and abiotic stress protectants and growth enhancers, are becoming increasingly important in agriculture also in the context of climate change. The search for new products that can help reduce chemical inputs under a variety of field conditions is the new challenge. In this study, we tested whether the combination of two microbial growth enhancers with complementary modes of action, 76A and T22, could facilitate tomato adaptation to a 30% reduction of optimal water and nitrogen requirements. The microbial inoculum increased tomato yield (+48.5%) under optimal water and nutrient conditions. In addition, the microbial application improved leaf water potential under stress conditions (+9.5%), decreased the overall leaf temperature (-4.6%), and increased shoot fresh weight (+15%), indicating that this consortium could act as a positive regulator of plant water relations under limited water and nitrogen availability. A significant increase in microbial populations in the rhizosphere with applications of 76A and T22 under stress conditions, suggested that these inoculants could enhance soil microbial abundance, including the abundance of native beneficial microorganisms. Sampling time, limited water and nitrogen regimes and microbial inoculations all affected bacterial and fungal populations in the rhizospheric soil. Overall, these results indicated that the selected microbial consortium could function as plant growth enhancer and stress protectant, possibly by triggering adaptation mechanisms via functional changes in the soil microbial diversity and relative abundance.
PubMed: 38126011
DOI: 10.3389/fpls.2023.1304627 -
The Journal of Chemical Physics Dec 2023The biological reduction of N2 to ammonia requires the ATP-dependent, sequential delivery of electrons from the Fe protein to the MoFe protein of nitrogenase. It has...
The biological reduction of N2 to ammonia requires the ATP-dependent, sequential delivery of electrons from the Fe protein to the MoFe protein of nitrogenase. It has been demonstrated that CdS nanocrystals can replace the Fe protein to deliver photoexcited electrons to the MoFe protein. Herein, light-activated electron delivery within the CdS:MoFe protein complex was achieved in the frozen state, revealing that all the electron paramagnetic resonance (EPR) active E-state intermediates in the catalytic cycle can be trapped and characterized by EPR spectroscopy. Prior to illumination, the CdS:MoFe protein complex EPR spectrum was composed of a S = 3/2 rhombic signal (g = 4.33, 3.63, and 2.01) consistent with the FeMo-cofactor in the resting state, E0. Illumination for sequential 1-h periods at 233 K under 1 atm of N2 led to a cumulative attenuation of E0 by 75%. This coincided with the appearance of S = 3/2 and S = 1/2 signals assigned to two-electron (E2) and four-electron (E4) reduced states of the FeMo-cofactor, together with additional S = 1/2 signals consistent with the formation of E6 and E8 states. Simulations of EPR spectra allowed quantification of the different E-state populations, along with mapping of these populations onto the Lowe-Thorneley kinetic scheme. The outcome of this work demonstrates that the photochemical delivery of electrons to the MoFe protein can be used to populate all of the EPR active E-state intermediates of the nitrogenase MoFe protein cycle.
Topics: Molybdoferredoxin; Quantum Dots; Temperature; Oxidation-Reduction; Nitrogenase; Electron Spin Resonance Spectroscopy; Azotobacter vinelandii
PubMed: 38117020
DOI: 10.1063/5.0170405 -
Plants (Basel, Switzerland) Nov 2023The huge development of climatic change highly affects our crop production and soil fertility. Also, the rise in the uncontrolled, excessive use of chemical fertilizers...
The huge development of climatic change highly affects our crop production and soil fertility. Also, the rise in the uncontrolled, excessive use of chemical fertilizers diminishes the soil prosperity and generates pollutants, threatening all environmental life forms, including us. Replacement of these chemical fertilizers with natural ones is becoming an inevitable environmental strategy. In our study, we evaluated the responses of L. to the action of single species and consortiums of plant growth-promoting bacteria (, , and ) in clay and new reclaimed soil types in terms of phenotype, yield components, and physiological and biochemical responses. Data analysis showed single or consortium microbial inoculation significantly increased the measured traits under clay and calcareous sandy soils compared to the control. Shoot physiological and biochemical activities, and seed biochemical activities were significantly enhanced with the inoculation of pea seeds with three types of bacteria in both soil types. The bud numbers, fresh weight, and seeds' dry weight increased in seeds treated with and in the sandy soil. Taken together, these findings suggested that the inoculation of plants with PGP bacteria could be used to diminish the implementation of chemical fertilizer and improve the goodness of agricultural products. These findings expand the understanding of the responsive mechanism of microbial inoculation under different soil types, especially at physiological and biochemical levels.
PubMed: 38068568
DOI: 10.3390/plants12233931 -
International Journal of... May 2024The growth, yield, and quality of cauliflower ( var. L.) cv. Pusa Snowball K-1 were studied using FeO-nano fertilizer (FeO-N) in combination with Azotobacter, Farmyard...
The growth, yield, and quality of cauliflower ( var. L.) cv. Pusa Snowball K-1 were studied using FeO-nano fertilizer (FeO-N) in combination with Azotobacter, Farmyard manure (FYM), and Phosphorus solubilizing bacteria (PSB). Hydrothermally synthesized FeO nanoparticles characterized with XRD, FTIR, and SEM. The experiment consisting 12 treatments viz. T (FeO-N), T comprising of FeO-N + FYM + + PSB, T (FeO-N + + PSB), T (FeO-N + FYM + ), T (FeO-N + FYM + PSB), T (FeO-N + FYM), T (FeO-N + ), T (FeO-N + PSB), T (PSB), T (), T (FYM), and T (control). FeO NPs positively enhance the photosynthetic activity and stimulate catalyze enzymatic action in plant leaves that effect the health of the plant and remarkably increase the crop yield. Application of FeO-nano fertilizer (FeO-N) along the , FYM, and PSB was shown encouraging growth effects to improve the cropping behavior. FeO NPs positively enhance the photosynthetic activity and stimulate catalyze enzymatic action in plant leaves that effect the health of the plant and remarkably increase the crop yield.
Topics: Brassica; Fertilizers; Plant Leaves; Azotobacter; Ferric Compounds; Biodegradation, Environmental; Phosphorus; Manure
PubMed: 38062781
DOI: 10.1080/15226514.2023.2288894 -
Carbohydrate Polymers Feb 2024Alginates are valued in many industries, due to their versatile properties. These polysaccharides originate from brown algae (Phaeophyceae) and some bacteria of the...
Alginates are valued in many industries, due to their versatile properties. These polysaccharides originate from brown algae (Phaeophyceae) and some bacteria of the Azotobacter and Pseudomonas genera, consisting of 1 → 4 linked β-d-mannuronic acid (M), and its C5-epimer α-l-guluronic acid (G). Several applications rely on a high G-content, which confers good gelling properties. Because of its high natural G-content (F = 0.60-0.75), the alginate from Laminaria hyperborea (LH) has sustained a thriving industry in Norway. Alginates from other sources can be upgraded with mannuronan C-5 epimerases that convert M to G, and this has been demonstrated in many studies, but not applied in the seaweed industry. The present study demonstrates epimerisation directly in the process of alginate extraction from cultivated Saccharina latissima (SL) and Alaria esculenta (AE), and the lamina of LH. Unlike conventional epimerisation, which comprises multiple steps, this in-process protocol can decrease the time and costs necessary for alginate upgrading. In-process epimerisation with AlgE1 enzyme enhanced G-content and hydrogel strength in all examined species, with the greatest effect on SL (F from 0.44 to 0.76, hydrogel Young's modulus from 22 to 34 kPa). As proof of concept, an upscaled in-process epimerisation of alginate from fresh SL was successfully demonstrated.
Topics: Laminaria; Alginates; Phaeophyceae; Hydrogels
PubMed: 38008481
DOI: 10.1016/j.carbpol.2023.121557 -
Plants (Basel, Switzerland) Nov 2023The enhancing effect of N-fixing bacterial strains in the presence of mineral N doses on maize plants in pots and field trials was investigated. The OT-H1 of 10 isolates...
The enhancing effect of N-fixing bacterial strains in the presence of mineral N doses on maize plants in pots and field trials was investigated. The OT-H1 of 10 isolates maintained the total nitrogen, nitrogenase activities, IAA production, and detection of NH in their cultures. In addition, they highly promoted the germination of maize grains in plastic bags compared to the remainder. Therefore, OT-H1 was subjected for identification and selected for further tests. Based on their morphological, cultural, and biochemical traits, they belonged to the genera . The genomic sequences of 16S rRNA were, thus, used to confirm the identification of the genera. Accordingly, the indexes of tree and similarity for the related bacterial species indicated that genera were exactly closely linked to strain OR512393. In pot (35 days) and field (120 days) trials, the efficiencies of both and SWERI 111 (sole/dual) with 100, 75, 50, and 25% mineral N doses were evaluated with completely randomized experimental design and three repetitions. Results indicated that N-fixing bacteria in the presence of mineral N treatment showed pronounced effects compared to controls. A high value of maize plants was also noticed through increasing the concentration of mineral N and peaked at a dose of 100%. Differences among N-fixing bacteria were insignificant and were observed for with different mineral N doses. Thus, the utilization of and in their dual mix in the presence of 75 followed by 50% mineral N was found to be the superior treatments, causing the enhancement of vegetative growth and grain yield parameters of maize plants. Additionally, proline and the enzyme activities of both polyphenol oxidase (PPO) and peroxidase (PO) of maize leaves were induced, and high protein contents of maize grains were accumulated due to the superior treatments. The utilization of such N-fixing bacteria was, therefore, found to be effective at improving soil fertility and to be an environmentally safe strategy instead, or at least with low doses, of chemical fertilizers.
PubMed: 38005727
DOI: 10.3390/plants12223830