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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 -
Asian Journal of Pharmaceutical Sciences May 2021Alginate is an edible heteropolysaccharide that abundantly available in the brown seaweed and the capsule of bacteria such as sp. and sp. Owing to alginate gel forming... (Review)
Review
Alginate is an edible heteropolysaccharide that abundantly available in the brown seaweed and the capsule of bacteria such as sp. and sp. Owing to alginate gel forming capability, it is widely used in food, textile and paper industries; and to a lesser extent in biomedical applications as biomaterial to promote wound healing and tissue regeneration. This is evident from the rising use of alginate-based dressing for heavily exuding wound and their mass availability in the market nowadays. However, alginate also has limitation. When in contact with physiological environment, alginate could gelate into softer structure, consequently limits its potential in the soft tissue regeneration and becomes inappropriate for the usage related to load bearing body parts. To cater this problem, wide range of materials have been added to alginate structure, producing sturdy composite materials. For instance, the incorporation of adhesive peptide and natural polymer or synthetic polymer to alginate moieties creates an improved composite material, which not only possesses better mechanical properties compared to native alginate, but also grants additional healing capability and promote better tissue regeneration. In addition, drug release kinetic and cell viability can be further improved when alginate composite is used as encapsulating agent. In this review, preparation of alginate and alginate composite in various forms (fibre, bead, hydrogel, and 3D-printed matrices) used for biomedical application is described first, followed by the discussion of latest trend related to alginate composite utilization in wound dressing, drug delivery, and tissue engineering applications.
PubMed: 34276819
DOI: 10.1016/j.ajps.2020.10.001 -
Journal of Applied Microbiology Oct 2022In the study, seven Plant Growth Promoting Rhizobacteria (PGPR) Azotobacter species were screened against three strains of Fusarium verticillioides to test its...
AIMS
In the study, seven Plant Growth Promoting Rhizobacteria (PGPR) Azotobacter species were screened against three strains of Fusarium verticillioides to test its antifungal activity. Azotobacter strains were tested for the degradation of fumonisin produced by F. verticillioides. Secondary metabolites were isolated and characterized from the Azotobacter strains for the first time.
METHODS AND RESULTS
Potential seven Azotobacter species antifungal activity was tested following the dual culture assay against three strains of Fusarium verticillioides namely FVM-42, FVM-86 and MTCC156 estimating the substantial zone of inhibition. Azotobacter species AZT-31 and AZT-50 strains significantly inhibited the growth of F. verticillioides recording drastic growth enhancement of maize under in-vitro conditions by calculating the infection incidence, vigour index and germination percentage. As confirmation, dereplication studies were conducted for the reconfirmation of Azotobacter strains by isolating from rhizoplane. Azotobacter strains played a key role in the degradation of fumonisin produced by F. verticillioides reporting 98% degradation at 2 h of incubation with the pathogen. Furthermore, in the study first time, we have tried to isolate and characterize the secondary metabolites from the Azotobacter strains exhibiting six compounds from the species AZT-31 (2) and AZT-50 (4). Preliminary in-vitro experiments were carried out using the compounds extracted to check the reduction of infection incidence (90%) and increase in germination percentage upto 50 to 70% when compared to the test pathogen.
CONCLUSION
Azotobacter strains referred as PGPR on influencing the growth of plant by producing certain substances that act as stimulators on inhibiting the growth of the pathogen.
SIGNIFICANCE AND IMPACT OF THE STUDY
The future perspective would be the production of an active combination of carboxamide compound and Azotobacter species for preventively controlling the phytopathogenic fungi of plants and crops and also towards the treatment of seeds.
Topics: Antifungal Agents; Azotobacter; Fumonisins; Fusarium; Zea mays
PubMed: 35809236
DOI: 10.1111/jam.15709 -
International Journal of Biological... Jul 2023Alginates are natural polysaccharides widely participating in food, pharmaceutical, and environmental applications due to their excellent gelling capacity. Their... (Review)
Review
Alginates are natural polysaccharides widely participating in food, pharmaceutical, and environmental applications due to their excellent gelling capacity. Their excellent biocompatibility and biodegradability further extend their application to biomedical fields. The low consistency in molecular weight and composition of algae-based alginates may limit their performance in advanced biomedical applications. It makes microbial alginate production more attractive due to its potential for customizing alginate molecules with stable characteristics. Production costs remain the primary factor limiting the commercialization of microbial alginates. However, carbon-rich wastes from sugar, dairy, and biodiesel industries may serve as potential substitutes for pure sugars for microbial alginate production to reduce substrate costs. Fermentation parameter control and genetic engineering strategies may further improve the production efficiency and customize the molecular composition of microbial alginates. To meet the specific needs of biomedical applications, alginates may need functionalization, such as functional group modifications and crosslinking treatments, to achieve enhanced mechanical properties and biochemical activities. The development of alginate-based composites incorporated with other polysaccharides, gelatin, and bioactive factors can integrate the advantages of each component to meet multiple requirements in wound healing, drug delivery, and tissue engineering applications. This review provided a comprehensive insight into the sustainable production of high-value microbial alginates. It also discussed recent advances in alginate modification strategies and alginate-based composites for representative biomedical applications.
Topics: Alginates; Pseudomonas; Azotobacter; Wound Healing; Tissue Engineering; Drug Delivery Systems; Fermentation; Gene Expression Regulation, Bacterial; Humans
PubMed: 37236570
DOI: 10.1016/j.ijbiomac.2023.125048 -
World Journal of Microbiology &... Apr 2022Bacterial cellulose (BC) is synthesized as a valuable extracellular biopolymer by several bacteria belonging to the genera of Acetobacter, Achromobacter,... (Review)
Review
Bacterial cellulose (BC) is synthesized as a valuable extracellular biopolymer by several bacteria belonging to the genera of Acetobacter, Achromobacter, Komagataeibacter, Agrobacterium, Bacillus, Azotobacter, Sarcinia, Lactobacillus and Gluconacetobacter. Unlike plant cellulose, since BC does not contain lignin, hemicellulose, pectin, arabinose and other plant-derived contaminants, it can be obtained purely from the culture media without any purification processes. BC exhibits excellent physicochemical and mechanical properties such as purity, high crystallinity, transparency, porosity, high water holding capacity, ultrafine nanoscale fiber network, tensile strength, high degree of polymerization, high surface area, chemical stability and proton conductivity. In addition, BC has become an essential nanomaterial in many industrial processes as it is biocompatible, biodegradable and renewable. In this respect, researchers are focused on the production of BC using low-cost substrates, investigation of potential BC producers, optimization of cultivation conditions, and modification of BC pellicles with different procedures. Based on these researches, this review of recent progress in bacterial cellulose production, both in vivo and in vitro modifications of surface properties of BC and its industrial applications in different areas are discussed in this review.
Topics: Bacteria; Cellulose; Culture Media; Fermentation; Lignin
PubMed: 35397756
DOI: 10.1007/s11274-022-03271-y -
Essays in Biochemistry Apr 2023Alginate is a polysaccharide consisting of β-D-mannuronate (M) and α-L-guluronate (G) produced by brown algae and some bacterial species. Alginate has a wide range of... (Review)
Review
Alginate is a polysaccharide consisting of β-D-mannuronate (M) and α-L-guluronate (G) produced by brown algae and some bacterial species. Alginate has a wide range of industrial and pharmaceutical applications, owing mainly to its gelling and viscosifying properties. Alginates with high G content are considered more valuable since the G residues can form hydrogels with divalent cations. Alginates are modified by lyases, acetylases, and epimerases. Alginate lyases are produced by alginate-producing organisms and by organisms that use alginate as a carbon source. Acetylation protects alginate from lyases and epimerases. Following biosynthesis, alginate C-5 epimerases convert M to G residues at the polymer level. Alginate epimerases have been found in brown algae and alginate-producing bacteria, predominantly Azotobacter and Pseudomonas species. The best characterised epimerases are the extracellular family of AlgE1-7 from Azotobacter vinelandii(Av). AlgE1-7 all consist of combinations of one or two catalytic A-modules and one to seven regulatory R-modules, but even though they are sequentially and structurally similar, they create different epimerisation patterns. This makes the AlgE enzymes promising for tailoring of alginates to have the desired properties. The present review describes the current state of knowledge regarding alginate-active enzymes with focus on epimerases, characterisation of the epimerase reaction, and how alginate epimerases can be used in alginate production.
Topics: Racemases and Epimerases; Alginates; Carbohydrate Epimerases; Azotobacter vinelandii; Lyases
PubMed: 36876890
DOI: 10.1042/EBC20220151 -
Biology Letters Mar 2022Declining food production in African agroecosystems is attributable to changes in weather patterns, soil infertility and limited farming inputs. The exploitation of...
Declining food production in African agroecosystems is attributable to changes in weather patterns, soil infertility and limited farming inputs. The exploitation of plant growth-promoting soil microbes could remedy these problems. Such microbes include ; free-living, nitrogen-fixing bacteria, which confer stress tolerance, avail phytohormones and aid in soil bioremediation. Here, we aimed to isolate, characterize and determine the biodiversity of native isolates from soils in semi-arid Eastern Kenya. Isolation was conducted on nitrogen-free Ashby's agar and the morphological, biochemical and molecular attributes evaluated. The isolates were sequenced using DNA amplicons of 27F and 1492R primers of the 16S rRNA gene loci. The Basic Local Alignment Search Tool (BLASTn) analysis of their sequences revealed the presence of three main species viz., and . Kitui County recorded the highest number of recovered isolates (45.4%) and lowest diversity index (0.8761). Tharaka Nithi County showed the lowest occurrence (26.36%) with a diversity index of (1.057). The diversity was influenced by the soil pH, texture and total organic content. This study reports for the first time a wide diversity of species from a semi-arid agroecosystem in Kenya with potential for utilization as low-cost, free-living nitrogen-fixing bioinoculant.
Topics: Azotobacter; Kenya; Nitrogen; RNA, Ribosomal, 16S; Soil; Soil Microbiology
PubMed: 35317624
DOI: 10.1098/rsbl.2021.0612 -
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 -
Chembiochem : a European Journal of... Jun 2020Nitrogen is one of the most important nutrients for plant growth. To enhance crop productivity, chemical nitrogen fertilizer is commonly applied in agriculture.... (Review)
Review
Nitrogen is one of the most important nutrients for plant growth. To enhance crop productivity, chemical nitrogen fertilizer is commonly applied in agriculture. Biological nitrogen fixation, the conversion of atmospheric N to NH , is an important source of nitrogen input in agriculture and represents a promising substitute for chemical nitrogen fertilizers. However, nitrogen fixation is only sporadically distributed within bacteria and archaea (diazotrophs). Thus, many biologists hope to reconstitute a nitrogenase biosynthetic pathway in a eukaryotic host, with the final aim of developing N -fixing cereal crops. With the advent of synthetic biology and a deep understanding of the fundamental genetic determinants necessary to sustain nitrogen fixation in bacteria, much progress has been made toward this goal. Transfer of native and refactored nif (nitrogen fixation) genes to non-diazotrophs has been attempted in model bacteria, yeast, and plants. Specifically, nif genes from Klebsiella oxytoca, Azotobacter vinelandii, and Paenibacillus polymyxa have been successfully transferred and expressed in Escherichia coli, Saccharomyces cerevisiae, and even in the tobacco plant. These advances have laid the groundwork to enable cereal crops to "fix" nitrogen themselves to sustain their growth and yield.
Topics: Azotobacter vinelandii; Escherichia coli; Klebsiella oxytoca; Nitrogen Fixation; Paenibacillus polymyxa; Saccharomyces cerevisiae; Nicotiana
PubMed: 32009294
DOI: 10.1002/cbic.201900784 -
PLoS Computational Biology Mar 2021The enzyme nitrogenase reduces dinitrogen to ammonia utilizing electrons, protons, and energy obtained from the hydrolysis of ATP. Mo-dependent nitrogenase is a...
The enzyme nitrogenase reduces dinitrogen to ammonia utilizing electrons, protons, and energy obtained from the hydrolysis of ATP. Mo-dependent nitrogenase is a symmetric dimer, with each half comprising an ATP-dependent reductase, termed the Fe Protein, and a catalytic protein, known as the MoFe protein, which hosts the electron transfer P-cluster and the active-site metal cofactor (FeMo-co). A series of synchronized events for the electron transfer have been characterized experimentally, in which electron delivery is coupled to nucleotide hydrolysis and regulated by an intricate allosteric network. We report a graph theory analysis of the mechanical coupling in the nitrogenase complex as a key step to understanding the dynamics of allosteric regulation of nitrogen reduction. This analysis shows that regions near the active sites undergo large-scale, large-amplitude correlated motions that enable communications within each half and between the two halves of the complex. Computational predictions of mechanically regions were validated against an analysis of the solution phase dynamics of the nitrogenase complex via hydrogen-deuterium exchange. These regions include the P-loops and the switch regions in the Fe proteins, the loop containing the residue β-188Ser adjacent to the P-cluster in the MoFe protein, and the residues near the protein-protein interface. In particular, it is found that: (i) within each Fe protein, the switch regions I and II are coupled to the [4Fe-4S] cluster; (ii) within each half of the complex, the switch regions I and II are coupled to the loop containing β-188Ser; (iii) between the two halves of the complex, the regions near the nucleotide binding pockets of the two Fe proteins (in particular the P-loops, located over 130 Å apart) are also mechanically coupled. Notably, we found that residues next to the P-cluster (in particular the loop containing β-188Ser) are important for communication between the two halves.
Topics: Adenosine Triphosphate; Azotobacter vinelandii; Binding Sites; Deuterium Exchange Measurement; Electron Transport; Models, Molecular; Molybdoferredoxin; Protein Binding
PubMed: 33661889
DOI: 10.1371/journal.pcbi.1008719