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Biology Nov 2023Iron is an essential nutrient for all life forms. Specialized mechanisms exist in bacteria to ensure iron uptake and its delivery to key enzymes within the cell, while... (Review)
Review
Iron is an essential nutrient for all life forms. Specialized mechanisms exist in bacteria to ensure iron uptake and its delivery to key enzymes within the cell, while preventing toxicity. Iron uptake and exchange networks must adapt to the different environmental conditions, particularly those that require the biosynthesis of multiple iron proteins, such as nitrogen fixation. In this review, we outline the mechanisms that the model diazotrophic bacterium uses to ensure iron nutrition and how it adapts Fe metabolism to diazotrophic growth.
PubMed: 37998022
DOI: 10.3390/biology12111423 -
The ISME Journal Dec 2023Nitrogen is a limiting nutrient for degraders function in hydrocarbon-contaminated environments. Biological nitrogen fixation by diazotrophs is a natural solution for...
Nitrogen is a limiting nutrient for degraders function in hydrocarbon-contaminated environments. Biological nitrogen fixation by diazotrophs is a natural solution for supplying bioavailable nitrogen. Here, we determined whether the diazotroph Azotobacter chroococcum HN can provide nitrogen to the polycyclic aromatic hydrocarbon-degrading bacterium Paracoccus aminovorans HPD-2 and further explored the synergistic interactions that facilitate pyrene degradation in nitrogen-deprived environments. We found that A. chroococcum HN and P. aminovorans HPD-2 grew and degraded pyrene more quickly in co-culture than in monoculture. Surface-enhanced Raman spectroscopy combined with N stable isotope probing (SERS - N SIP) demonstrated that A. chroococcum HN provided nitrogen to P. aminovorans HPD-2. Metabolite analysis and feeding experiments confirmed that cross-feeding occurred between A. chroococcum HN and P. aminovorans HPD-2 during pyrene degradation. Transcriptomic and metabolomic analyses further revealed that co-culture significantly upregulated key pathways such as nitrogen fixation, aromatic compound degradation, protein export, and the TCA cycle in A. chroococcum HN and quorum sensing, aromatic compound degradation and ABC transporters in P. aminovorans HPD-2. Phenotypic and fluorescence in situ hybridization (FISH) assays demonstrated that A. chroococcum HN produced large amounts of biofilm and was located at the bottom of the biofilm in co-culture, whereas P. aminovorans HPD-2 attached to the surface layer and formed a bridge-like structure with A. chroococcum HN. This study demonstrates that distinct syntrophic interactions occur between A. chroococcum HN and P. aminovorans HPD-2 and provides support for their combined use in organic pollutant degradation in nitrogen-deprived environments.
Topics: Nitrogen; In Situ Hybridization, Fluorescence; Nitrogen Fixation; Pyrenes
PubMed: 37775536
DOI: 10.1038/s41396-023-01522-w -
MBio Jun 2024Life depends on a conserved set of chemical energy currencies that are relics of early biochemistry. One of these is ATP, a molecule that, when paired with a divalent...
Life depends on a conserved set of chemical energy currencies that are relics of early biochemistry. One of these is ATP, a molecule that, when paired with a divalent metal ion such as Mg, can be hydrolyzed to support numerous cellular and molecular processes. Despite its centrality to extant biochemistry, it is unclear whether ATP supported the function of ancient enzymes. We investigate the evolutionary necessity of ATP by experimentally reconstructing an ancestral variant of the N-reducing enzyme nitrogenase. The Proterozoic ancestor is predicted to be ~540-2,300 million years old, post-dating the Great Oxidation Event. Growth rates under nitrogen-fixing conditions are ~80% of those of wild type in . In the extant enzyme, the hydrolysis of two MgATP is coupled to electron transfer to support substrate reduction. The ancestor has a strict requirement for ATP with no other nucleotide triphosphate analogs (GTP, ITP, and UTP) supporting activity. Alternative divalent metal ions (Fe, Co, and Mn) support activity with ATP but with diminished activities compared to Mg, similar to the extant enzyme. Additionally, it is shown that the ancestor has an identical efficiency in ATP hydrolyzed per electron transferred to the extant of two. Our results provide direct laboratory evidence of ATP usage by an ancient enzyme.IMPORTANCELife depends on energy-carrying molecules to power many sustaining processes. There is evidence that these molecules may predate the rise of life on Earth, but how and when these dependencies formed is unknown. The resurrection of ancient enzymes provides a unique tool to probe the enzyme's function and usage of energy-carrying molecules, shedding light on their biochemical origins. Through experimental reconstruction, this research investigates the ancestral dependence of a nitrogen-fixing enzyme on the energy carrier ATP, a requirement for function in the modern enzyme. We show that the resurrected ancestor does not have generalist nucleotide specificity. Rather, the ancestor has a strict requirement for ATP, like the modern enzyme, with similar function and efficiency. The findings elucidate the early-evolved necessity of energy-yielding molecules, delineating their role in ancient biochemical processes. Ultimately, these insights contribute to unraveling the intricate tapestry of evolutionary biology and the origins of life-sustaining dependencies.
PubMed: 38869277
DOI: 10.1128/mbio.01271-24 -
Molecular Plant-microbe Interactions :... Sep 2023spp. make up 1.6% of the bacteria in the soil and are found throughout the world. More than 140 species of this genus have been identified, some beneficial to the...
spp. make up 1.6% of the bacteria in the soil and are found throughout the world. More than 140 species of this genus have been identified, some beneficial to the plant. Several species in the family Pseudomonadaceae, including AvOP, A1501, DSM4166, 6HT33bT, and sp. strain K1 can fix nitrogen from the air. The genes required for these reactions are organized in a nitrogen fixation island, obtained via horizontal gene transfer from , , and . Today, this island is conserved in spp. from different geographical locations, which, in turn, have evolved to deal with different geo-climatic conditions. Here, we summarize the molecular mechanisms behind -driven plant growth promotion, with particular focus on improving plant performance at limiting nitrogen (N) and improving plant N content. We describe -plant interaction strategies in the soil, noting that the mechanisms of denitrification, ammonification, and secondary metabolite signaling are only marginally explored. Plant growth promotion is dependent on the abiotic conditions and differs at sufficient and deficient N. The molecular controls behind different plant responses are not fully elucidated. We suggest that superposition of transcriptome, proteome, and metabolome data and their integration with plant phenotype development through time will help fill these gaps. The aim of this review is to summarize the knowledge behind -driven nitrogen fixation and to point to possible agricultural solutions. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.
PubMed: 36989040
DOI: 10.1094/MPMI-10-22-0223-CR -
PeerJ 2023The raising trend of cultivation of ()-transgenic cotton is faced with a new challenge what effects on the growth and yield of cotton under elevated CO.
BACKGROUND
The raising trend of cultivation of ()-transgenic cotton is faced with a new challenge what effects on the growth and yield of cotton under elevated CO.
METHODS
Rhizobacteria is the significant biological regulator to increase environmental suitability and ameliorate soil-nitrogen utilization efficiency of crops, especially cotton. Pot-culture experiments investigated the effects on the yield and fiber quality components of cotton (transgenic Line SCRC 37) inoculated with (AC) under elevated CO.
RESULTS
The findings indicated that the inoculation of azotobacter significantly improved the yield and fiber quality components of cotton, the elevated CO significantly increased the soil density of and the partial yield indexes (as cottonweightper 20 bolls, lint yield per 20 bolls and boll number per plant), and non-significant decrease the fiber quality components of cotton except uniform.
DISCUSSION
Overall results obviously depicted that the inoculation of azotobacter and the elevated CO had positive effects on the yield and fiber quality components of cotton. Presumably, azotobacter inoculation can be used to stimulate plant soil-nitrogen uptake and promote plant growth for cotton under elevated CO in the future.
Topics: Bacillus thuringiensis; Carbon Dioxide; Azotobacter; Soil; Gossypium; Nitrogen
PubMed: 37576495
DOI: 10.7717/peerj.15811 -
Plants (Basel, Switzerland) Aug 2023The problem of phosphorus and nitrogen deficiency in agricultural soils has been solved by adding chemical fertilizers. However, their excessive use and their...
The problem of phosphorus and nitrogen deficiency in agricultural soils has been solved by adding chemical fertilizers. However, their excessive use and their accumulation have only contributed to environmental contamination. Given the high content of nutrients in biosolids collected from a food industry waste treatment plant, their use as fertilizers was investigated in plants grown in sandy loam soil collected from a semi-desert area. These biosolids contained insoluble phosphorus sources; therefore, given the ability of to solubilize phosphates, this strain was incorporated into the study. In vitro, the suitable conditions for the growth of plants were determined by using biosolids as a fertilizer and as a plant-growth-promoting microorganism; in vitro, the ability of to solubilize phosphates, fix nitrogen, and produce indole acetic acid, a phytohormone that promotes root formation, was also evaluated. At the greenhouse stage, the plants fertilized with biosolids at concentrations of 15 and 20% (/) and inoculated with favored the development of bending strength plants, which was observed on the increased stem diameter (>13.5% compared with the negative control and >7.4% compared with the positive control), as well as a better absorption of phosphorus and nitrogen, the concentration of which increased up to 62.8% when compared with that in the control treatments. The interactions between plants and were observed via scanning electron microscopy. The application of biosolids and in plants grown in greenhouses presented better development than when plants were treated with a chemical fertilizer. The enhanced plant growth was attributed to the increase in root surface area.
PubMed: 37687299
DOI: 10.3390/plants12173052 -
Research Square Nov 2023The increasing global demand for food, coupled with concerns about the environmental impact of synthetic fertilizers, underscores the urgency of developing sustainable...
The increasing global demand for food, coupled with concerns about the environmental impact of synthetic fertilizers, underscores the urgency of developing sustainable agricultural practices. Nitrogen-fixing bacteria, known as diazotrophs, offer a potential solution by converting atmospheric nitrogen into bioavailable forms, reducing the reliance on synthetic fertilizers. However, a deeper understanding of their interactions with plants and other microbes is needed. In this study, we introduce a recently developed label-free 3D quantitative phase imaging technology called dynamic quantitative oblique back-illumination microscopy (DqOBM) to assess the dynamic activity of diazotrophs and . Our experiments involved three different diazotrophs (, , and ) cultured on media with amendments of carbon and nitrogen sources. Over five days, we observed increased dynamic activity in nutrient-amended media. These results suggest that the observed bacterial dynamics correlate with their metabolic activity. Furthermore, we applied qOBM to visualize bacterial activity within the root cap and elongation zone of primary roots. This allowed us to identify distinct areas of microbial infiltration in plant roots without the need for fluorescent markers. Our findings demonstrate that DqOBM can effectively characterize microbial activity and provide insights into plant-microbe interactions , offering a valuable tool for advancing our understanding of sustainable agriculture.
PubMed: 37961396
DOI: 10.21203/rs.3.rs-3517586/v1 -
Plants (Basel, Switzerland) Aug 2023Calcareous soil had sufficient phosphorus and potassium (PK) in different forms due to the high contents of PK-bearing minerals; however, the available PK state was...
Compost and Phosphorus/Potassium-Solubilizing Fungus Effectively Boosted Quinoa's Physio-Biochemical Traits, Nutrient Acquisition, Soil Microbial Community, and Yield and Quality in Normal and Calcareous Soils.
Calcareous soil had sufficient phosphorus and potassium (PK) in different forms due to the high contents of PK-bearing minerals; however, the available PK state was reduced due to its PK-fixation capacity. Compost, coupled with high PK solubilization capacity microbes, is a sustainable solution for bioorganic fertilization of plants grown in calcareous soil. A 2-year field experiment was conducted to investigate the effect of compost (20 t ha) with through soil drenching (C-AN) along with partial substitution of PK fertilization on quinoa performance in normal and calcareous soils. Treatments included PK (72 kg PO ha + 60 kg KO ha as conventional rate), PK+C-AN, PK+C-AN, PK+C-AN, PK+C-AN, and only C-AN in normal and calcareous soils. Results showed that C-AN and reduced PK fertilization (up to 75 or 50%) increased photosynthetic pigments and promoted nutrient acquisition in quinoa grown in calcareous soil. Reduced PK fertilization to 75 or 50% plus C-AN in calcareous soil increased osmoprotectants, nonenzymatic antioxidants, and DPPH scavenging activity of quinoa's leaves compared to the PK+C-AN treatment. The integrative application of high PK levels and C-AN enhanced the quinoa's seed nutritional quality (i.e., lipids, carbohydrates, mineral contents, total phenolics, total flavonoids, half maximal inhibitory concentration, and antiradical power) in calcareous soil. At reduced PK fertilization (up to 75 or 50%), application of compost with through soil drenching increased plant dry weight by 38.7 or 53.2%, hectoliter weight by 3.0 or 2.4%, seed yield by 49.1 or 39.5%, and biological yield by 43.4 or 33.6%, respectively, compared to PK+C-AN in calcareous soil. The highest P-solubilizing microorganism's population was found at PK+C-AN in calcareous soil, while the highest sp. population was observed under high PK levels + C-AN in normal soil. Our study recommends that compost with as a bioorganic fertilization treatment can partially substitute PK fertilization and boost quinoa's tolerance to salt calcareous-affected soil.
PubMed: 37687318
DOI: 10.3390/plants12173071 -
NRT1.1B mediates rice plant growth and soil microbial diversity under different nitrogen conditions.AMB Express Apr 2024Interactions between microorganisms and plants can stimulate plant growth and promote nitrogen cycling. Nitrogen fertilizers are routinely used in agriculture to improve...
Interactions between microorganisms and plants can stimulate plant growth and promote nitrogen cycling. Nitrogen fertilizers are routinely used in agriculture to improve crop growth and yield; however, poor use efficiency impairs the optimal utilization of such fertilizers. Differences in the microbial diversity and plant growth of rice soil under different nitrogen application conditions and the expression of nitrogen-use efficiency-related genes have not been previously investigated. Therefore, this study investigates how nitrogen application and nitrogen-use efficiency-related gene NRT1.1B expression affect the soil microbial diversity and growth indices of two rice varieties, Huaidao 5 and Xinhuai 5. In total, 103,463 and 98,427 operational taxonomic units were detected in the soils of the Huaidao 5 and Xinhuai 5 rice varieties, respectively. The Shannon and Simpson indices initially increased and then decreased, whereas the Chao and abundance-based coverage estimator indices decreased after the application of nitrogen fertilizer. Nitrogen fertilization also reduced soil bacterial diversity and richness, as indicated by the reduced abundances of Azotobacter recorded in the soils of both rice varieties. Nitrogen application initially increased and then decreased the grain number per panicle, yield per plant, root, stem, and leaf nitrogen, total nitrogen content, glutamine synthetase, nitrate reductase, urease, and root activities of both varieties. Plant height showed positive linear trends in response to nitrogen application, whereas thousand-grain weights showed a negative trend. Our findings may be used to optimize nitrogen fertilizer use for rice cultivation and develop crop-variety-specific strategies for nitrogen fertilizer application.
PubMed: 38647736
DOI: 10.1186/s13568-024-01683-7 -
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