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Proceedings of the National Academy of... Mar 2021Nitrogenases utilize Fe-S clusters to reduce N to NH The large number of Fe sites in their catalytic cofactors has hampered spectroscopic investigations into their...
Nitrogenases utilize Fe-S clusters to reduce N to NH The large number of Fe sites in their catalytic cofactors has hampered spectroscopic investigations into their electronic structures, mechanisms, and biosyntheses. To facilitate their spectroscopic analysis, we are developing methods for incorporating Fe into specific sites of nitrogenase cofactors, and we report herein site-selective Fe labeling of the L-cluster-a carbide-containing, [FeSC] precursor to the Mo nitrogenase catalytic cofactor. Treatment of the isolated L-cluster with the chelator ethylenediaminetetraacetate followed by reconstitution with Fe results in Fe labeling of the terminal Fe sites in high yield and with high selectivity. This protocol enables the generation of L-cluster samples in which either the two terminal or the six belt Fe sites are selectively labeled with Fe. Mössbauer spectroscopic analysis of these samples bound to the nitrogenase maturase NifX reveals differences in the primary coordination sphere of the terminal Fe sites and that one of the terminal sites of the L-cluster binds to H35 of NifX. This work provides molecular-level insights into the electronic structure and biosynthesis of the L-cluster and introduces postbiosynthetic modification as a promising strategy for studies of nitrogenase cofactors.
Topics: Azotobacter vinelandii; Electron Spin Resonance Spectroscopy; Molybdoferredoxin; Nitrogenase; Protein Precursors; Spectroscopy, Mossbauer
PubMed: 33836573
DOI: 10.1073/pnas.2015361118 -
Journal of Microbiological Methods Jul 2024The present study was carried out to valorise cereal (rice and wheat) bran for the development of low-cost liquid consortium bioformulation. Different concentrations of...
Novel cereal bran based low-cost liquid medium for enhanced growth, multifunctional traits and shelf life of consortium biofertilizer containing Azotobacter chroococcum, Bacillus subtilis and Pseudomonas sp.
The present study was carried out to valorise cereal (rice and wheat) bran for the development of low-cost liquid consortium bioformulation. Different concentrations of bran-based liquid media formulations were evaluated for the growth of consortium biofertilizer cultures (Azotobacter chroococcum, Bacillus subtilis and Pseudomonas sp.). Among the bran-based formulations, wheat bran-based formulation WB5, exhibited the highest viable cell of 10.68 ± 0.09 Log CFU/ml and 12.63 ± 0.04 Log CFU/ml for Azotobacter chroococcum and Bacillus subtilis whereas for Pseudomonas sp., rice bran based bioformulation RB5 recorded maximum viability (12.71 ± 0.05 Log CFU/ml) after 72 h of incubation. RB5 and WB5liquid formulations were further optimized for enhanced shelf life using 5, 10 and 15 mM of trehalose, 0.05 and 0.1% carboxymethyl cellulose, and 0.5 and 1.0% glycerol. Following the peak growth at 72 h of incubation, a gradual decrease in the viable population of consortium biofertilizer cultures was observed in all the liquid formulations. The WB5 and RB5 formulations with 15 mM trehalose and 0.1% CMC, not only recorded significantly highest cell count of consortium biofertilizer cultures, but also maximally supported multi-functional traits i.e., phosphate and zinc solubilization, ammonia and IAA production up to 150 days. Further evaluation of seedling emergence and growth of wheat (PBW 826) under axenic conditions recorded WB5 amended with 15 mM trehalose-based consortium bioformulation to exhibit maximum emergence and growth of wheat seedlings. This low-cost liquid formulation can be used for large-scale biofertilizer production as a cost-effective liquid biofertilizer production technology.
Topics: Bacillus subtilis; Pseudomonas; Azotobacter; Fertilizers; Dietary Fiber; Culture Media; Oryza; Edible Grain; Microbial Viability
PubMed: 38740286
DOI: 10.1016/j.mimet.2024.106952 -
PloS One 2018Safflower is an important industrial oil seed and bioenergy crop in semi-arid subtropical regions due to its potential to grow on marginal land and having good...
Safflower is an important industrial oil seed and bioenergy crop in semi-arid subtropical regions due to its potential to grow on marginal land and having good percentage of seed oil contents which is an important parameter for biofuel production. However, it is an ignored crop in Pakistan. In order to improve the crop productivity and reduce the use of agrochemicals for sustainable biodiesel feedstock production, an experiment was conducted for two years to improve the fatty acid composition and oil quality of Carthamus tinctorius L. (safflower) by the inoculation of Azospirillum and Azotobacter alone as well as in combined application with nitrogen and phosphate (NP) fertilizers on cultivars Thori and Saif-32 under field conditions. Separation and quantification of fatty acids were done on precise comprehensive two-dimensional gas chromatography (GC×GC). The results showed that fatty acid profile specifically monounsaturated fatty acids i-e oleic acid (C18:1) was significantly improved by Azospirillum supplemented with the quarter dose of NP fertilizers (SPQ) with concomitant decrease in polyunsaturated fatty acids by the respective treatment. Oil quality attributes such as acid value, saponification number, iodine value, refractive index and free fatty acid contents were reduced by the application of Azotobacter and Azospirillum in combination with half and quarter doses of NP fertilizers treatments (BTH, SPH, BTQ and SPQ). The reduction in these variables is positively linked with improved biodiesel yield and quality. It can be concluded that application of Azospirillum and Azotobacter not only reduced the use of NP fertilizers up to 50%-75% but also improved the oil quality in order to obtain environment friendly, sustainable and green fuel.
Topics: Agriculture; Azospirillum; Azotobacter; Biofuels; Carthamus tinctorius; Fatty Acids; Fertilizers; Nitrogen; Phosphates; Safflower Oil; Soil Microbiology; Species Specificity
PubMed: 30096207
DOI: 10.1371/journal.pone.0201738 -
Pakistan Journal of Biological Sciences... Jan 2020The Damping-off disease is one of the most reasons for low productively of tomato in the world, especially in Iraq. In the current study, two types of bacteria...
BACKGROUND AND OBJECTIVE
The Damping-off disease is one of the most reasons for low productively of tomato in the world, especially in Iraq. In the current study, two types of bacteria (Azotobacter chroococcum and Pseudomonas fluorescens) were used to evaluate their efficacy in inhibiting the growth of pathogenic fungi Rhizoctonia solani and Fusarium solani and protecting the seeds of tomato and increasing their germination percentage.
MATERIALS AND METHODS
Dual culture technique and Food poisoning technique were used to study the effect of bacteria on the growth of fungi understudy, and study the effect of bacterial filtrates on germination of tomato seeds.
RESULTS
A. chroococcum showed the strongest antagonistic activity followed by P. fluorescens with the percentage of inhibition ranging between 72.9-77.1 and 69.5-70.3% for R. solani and F. solani respectively after 7 days of incubation. The effect of A. chroococcum and P. fluorescens filtrates were increased and also increased the inhibition of growth of fungi understudy, A. chroococcum filtrate also showed the strongest inhibitory effect followed by P. fluorescens with the percentage of inhibition ranging between 86.0-87.0 and 83.0-83.5% for R. solani and F. solani respectively at 20% concentration of filtrate. The percentage of seeds germination reached 90% in the treatment of A. chroococcum filtrate and 80% in the treatment of P. fluorescens filtrate.
CONCLUSION
It can be concluded that the filtrates of A. chroococcum and P. fluorescens have antifungal properties against R. solani and F. solani and provided a high protection and increasing tomato seeds germination percentage.
Topics: Azotobacter; Crops, Agricultural; Fusarium; Germination; Solanum lycopersicum; Pest Control, Biological; Plant Diseases; Pseudomonas fluorescens; Rhizoctonia
PubMed: 33274875
DOI: 10.3923/pjbs.2020.1456.1461 -
Scientific Reports Sep 2015Microbial communities in rhizosphere interact with each other and form a basis of a cumulative impact on plant growth. Rhizospheric microorganisms like Piriformospora...
Microbial communities in rhizosphere interact with each other and form a basis of a cumulative impact on plant growth. Rhizospheric microorganisms like Piriformospora indica and Azotobacter chroococcum are well known for their beneficial interaction with plants. These features make P. indica/A. chroococcum co-inoculation of crops most promising with respect to sustainable agriculture and to understanding the transitions in the evolution of rhizospheric microbiome. Here, we investigated interactions of P. indica with A. chroococcum in culture. Out of five Azotobacter strains tested, WR5 exhibited growth-promoting while strain M4 exerted growth-inhibitory effect on the fungus in axenic culture. Electron microscopy of co-culture indicated an intimate association of the bacterium with the fungus. 2-D gel electrophoresis followed by mass spectrometry of P. indica cellular proteins grown with or without WR5 and M4 showed differential expression of many metabolic proteins like enolase-I, ureaseD, the GTP binding protein YPT1 and the transmembrane protein RTM1. Fungal growth as influenced by bacterial crude metabolites was also monitored. Taken together, the results conform to a model where WR5 and M4 influence the overall growth and physiology of P. indica which may have a bearing on its symbiotic relationship with plants.
Topics: Azotobacter; Basidiomycota; Fungal Proteins; Microbial Interactions; Proteome; Proteomics; Secondary Metabolism
PubMed: 26350628
DOI: 10.1038/srep13911 -
Genes Feb 2022CbrAB is a two-component system, unique to bacteria of the family , capable of integrating signals and involved in a multitude of physiological processes that allow... (Review)
Review
CbrAB is a two-component system, unique to bacteria of the family , capable of integrating signals and involved in a multitude of physiological processes that allow bacterial adaptation to a wide variety of varying environmental conditions. This regulatory system provides a great metabolic versatility that results in excellent adaptability and metabolic optimization. The two-component system (TCS) CbrA-CbrB is on top of a hierarchical regulatory cascade and interacts with other regulatory systems at different levels, resulting in a robust output. Among the regulatory systems found at the same or lower levels of CbrAB are the NtrBC nitrogen availability adaptation system, the Crc/Hfq carbon catabolite repression cascade in , or interactions with the GacSA TCS or alternative sigma ECF factor, such as SigX. The interplay between regulatory mechanisms controls a number of physiological processes that intervene in important aspects of bacterial adaptation and survival. These include the hierarchy in the use of carbon sources, virulence or resistance to antibiotics, stress response or definition of the bacterial lifestyle. The multiple actions of the CbrAB TCS result in an important competitive advantage.
Topics: Bacterial Proteins; Carbon; Gene Expression Regulation, Bacterial; Nitrogen; Pseudomonas
PubMed: 35205417
DOI: 10.3390/genes13020375 -
Microbial Ecology Nov 2023The introduction of legumes into rotations can improve nitrogen use efficiency and crop yield; however, its microbial mechanism involved remains unclear. This study...
The introduction of legumes into rotations can improve nitrogen use efficiency and crop yield; however, its microbial mechanism involved remains unclear. This study aimed to explore the temporal impact of peanut introduction on microorganisms related to nitrogen metabolism in rotation systems. In this study, the dynamics of diazotrophic communities in two crop seasons and wheat yields of two rotation systems: winter wheat - summer maize (WM) and spring peanut → winter wheat - summer maize (PWM) in the North China Plain were investigated. Our results showed that peanut introduction increased wheat yield and biomass by 11.6% (p < 0.05) and 8.9%, respectively. Lower Chao1 and Shannon indexes of the diazotrophic communities were detected in soils that sampling in June compared with those sampling in September, although no difference was found between WM and PWM. Principal co-ordinates analysis (PCoA) showed that rotation system significantly changed the diazotrophic community structures (PERMANOVA; p < 0.05). Compared with WM, the genera of Azotobacter, Skermanella, Azohydromonas, Rhodomicrobium, Azospirillum, Unclassified_f_Opitutaceae, and Unclassified_f_Rhodospirillaceae were significantly enriched (p < 0.05) in PWM. Furthermore, rotation system and sampling time significantly influenced soil properties, which significantly correlated with the top 15 genera in relative abundance. Partial least squares path modeling (PLS-PM) analysis further showed that the diazotrophic community diversity (alpha- and beta-diversity) and soil properties (pH, SOC and TN) significantly affected wheat yield. In conclusion, legume inclusion has the potential to stabilize diazotrophic community structure at the temporal scales and increase subsequent crop yield.
Topics: Agriculture; Arachis; Triticum; Soil; Fabaceae; Nitrogen
PubMed: 37296336
DOI: 10.1007/s00248-023-02254-2 -
Metallomics : Integrated Biometal... Jan 2019To increase iron (Fe) bioavailability in surface soils, microbes secrete siderophores, chelators with widely varying Fe affinities. Strains of the soil bacterium...
To increase iron (Fe) bioavailability in surface soils, microbes secrete siderophores, chelators with widely varying Fe affinities. Strains of the soil bacterium Azotobacter chroococcum (AC), plant-growth promoting rhizobacteria used as agricultural inoculants, require high Fe concentrations for aerobic respiration and nitrogen fixation. Recently, A. chroococcum str. NCIMB 8003 was shown to synthesize three siderophore classes: (1) vibrioferrin, a low-affinity α-hydroxy carboxylate (pFe = 18.4), (2) amphibactins, high-affinity tris-hydroxamates, and (3) crochelin A, a high-affinity siderophore with mixed Fe-chelating groups (pFe = 23.9). The relevance and specific functions of these siderophores in AC strains remain unclear. We analyzed the genome and siderophores of a second AC strain, A. chroococcum str. B3, and found that it also produces vibrioferrin and amphibactins, but not crochelin A. Genome comparisons indicate that vibrioferrin production is a vertically inherited, conserved strategy for Fe uptake in A. chroococcum and other species of Azotobacter. Amphibactin and crochelin biosynthesis reflects a more complex evolutionary history, shaped by vertical gene transfer, gene gain and loss through recombination at a genomic hotspot. We found conserved patterns of low vs. high-affinity siderophore production across strains: the low-affinity vibrioferrin was produced by mildly Fe limited cultures. As cells became more severely Fe starved, vibrioferrin production decreased in favor of high-affinity amphibactins (str. B3, NCIMB 8003) and crochelin A (str. NCIMB 8003). Our results show the evolution of low and high-affinity siderophore families and conserved patterns for their production in response to Fe bioavailability in a common soil diazotroph.
Topics: Azotobacter; Bacterial Proteins; Biosynthetic Pathways; Evolution, Molecular; Genes, Bacterial; Genomics; Nitrogen; Nitrogen Fixation; Phylogeny; Siderophores; Soil Microbiology
PubMed: 30444515
DOI: 10.1039/c8mt00236c -
International Journal of Systematic and... Jul 2019A Gram-stain-negative, aerobic, nitrogen-fixing bacterium, designated strain L461, was isolated from leaves of Bryophyllum pinnatum growing at the South China...
A Gram-stain-negative, aerobic, nitrogen-fixing bacterium, designated strain L461, was isolated from leaves of Bryophyllum pinnatum growing at the South China Agricultural University. Phylogenetic analysis of the 16S rRNA gene sequence indicated it as a member of the genus Azotobacter closely related to Azotobacter beijerinckii JCM 20725 (97.82 % similarity) and Azotobacter chroococcum ATCC 9043 (97.34 %). Its major fatty acid components were C16 : 1 ω9c and C16 : 0. Its predominant isoprenoid quinone was Q-9. Its major polar lipids were phosphatidylethanolamine, phosphatidylglycerol, aminophospholipid, phospholipid and one unknown lipid. Its DNA G+C content was 64.9 mol% (Tm). DNA-DNA relatedness values between strain L461 and the reference strains of A. beijerinckii and A. chroococcum were 46.43 and 28.23 %, respectively. Biological and biochemical tests, protein patterns, genomic DNA fingerprinting, and comparison of cellular fatty acids distinguished strain L461 from the closely related Azotobacter species. Based on these data, the novel species Azotobacter bryophylli sp. nov. is proposed, with the type strain L461 (=KCTC 62195=GDMCC 1.1250).
Topics: Azotobacter; Bacterial Typing Techniques; Base Composition; China; DNA Fingerprinting; DNA, Bacterial; Fatty Acids; Kalanchoe; Nucleic Acid Hybridization; Phospholipids; Phylogeny; Plant Leaves; RNA, Ribosomal, 16S; Sequence Analysis, DNA; Ubiquinone
PubMed: 31046894
DOI: 10.1099/ijsem.0.003412 -
PloS One 2017The effects of adding the biosurfactant rhamnolipid, the lignolytic and cellulolytic fungus Phanerochete chrysosporium, and the free-living nitrogen-fixing bacterium...
The effects of adding the biosurfactant rhamnolipid, the lignolytic and cellulolytic fungus Phanerochete chrysosporium, and the free-living nitrogen-fixing bacterium Azotobacter chrococcum on vermicomposting of green waste with Eisenia fetida was investigated. The addition of rhamnolipid and/or either microorganism alone or in all combinations significantly increased E. fetida growth rate, the number of E. fetida juveniles and cocoons, the population densities of cellulolytic fungi and Azotobacter bacteria, and cellulase and urease activities in the vermicomposts. The quality of the final vermicompost (in terms of electrical conductivity, nutrient content, C/N ratio, humic acid content, lignin and cellulose contents, and phytotoxicity to germinating seeds) was enhanced by addition of rhamnolipid and/or microorganisms. The physical characteristics of vermicomposts produced with rhamnolipid and/or microorganisms were acceptable for agricultural application. The best quality vermicompost was obtained with the combined addition of P. chrysosporium, A. chrococcum, and rhamnolipid.
Topics: Agricultural Inoculants; Animals; Biodegradation, Environmental; Glycolipids; Manure; Oligochaeta; Soil
PubMed: 28122059
DOI: 10.1371/journal.pone.0170820