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World Journal of Microbiology &... Feb 2016As obligate aerobic soil organisms, the ability of Azotobacter species to fix nitrogen is unusual given that the nitrogenase complex requires a reduced cellular... (Review)
Review
As obligate aerobic soil organisms, the ability of Azotobacter species to fix nitrogen is unusual given that the nitrogenase complex requires a reduced cellular environment. Molecular hydrogen is an unavoidable byproduct of the reduction of dinitrogen; at least one molecule of H2 is produced for each molecule of N2 fixed. This could be considered a fault in nitrogenase efficiency, essentially a waste of energy and reducing equivalents. Wild-type Azotobacter captures this hydrogen and oxidizes it with its membrane-bound uptake hydrogenase complex. Strains lacking an active hydrogenase complex have been investigated for their hydrogen production capacities. What is the role of H2 in the energy metabolism of nitrogen-fixing Azotobacter? Is hydrogen production involved in Azotobacter species' protection from or tolerance to oxygen, or vice versa? What yields of hydrogen can be expected from hydrogen-evolving strains? Can the yield of hydrogen be controlled or increased by changing genetic, environmental, or physiological conditions? We will address these questions in the following mini-review.
Topics: Azotobacter; Heterotrophic Processes; Hydrogen; Oxidation-Reduction; Protons; Soil Microbiology
PubMed: 26748806
DOI: 10.1007/s11274-015-1980-5 -
Journal of Bacteriology Aug 1979Batch cultures of Azotobacter vinelandii grown in phosphate-deficient media were compared with control cultures grown in phosphate-sufficient media. Phosphate limitation...
Batch cultures of Azotobacter vinelandii grown in phosphate-deficient media were compared with control cultures grown in phosphate-sufficient media. Phosphate limitation was assessed by total cell yield and by growth kinetics. Although cell protein, nucleic acids, and early growth rate were unaffected by phosphate deficiency, cell wall structure, oxygen uptake, and cell viability were significantly affected. Also, phosphate-limited cells contained much larger amounts of poly-beta-hydroxybutyric acid but lower adenylate nucleotide energy charge than did control cells. The ratio of adenosine 5'-triphosphate to adenosine 5'-diphosphate was much lower in phosphate-deficient cells. The data indicate a substrate saving choice of three metabolic pathways available to this organism under different growth conditions.
Topics: Adenine Nucleotides; Azotobacter; Bacterial Proteins; Cell Wall; DNA, Bacterial; Hydroxybutyrates; Oxygen Consumption; Phosphates; RNA, Bacterial
PubMed: 457614
DOI: 10.1128/jb.139.2.639-645.1979 -
Microbiological Research Sep 2022In the present study Piriformospora indica (Pi) a phyto-promotional fungus and Azotobacter chroococcumWR5 (AzWR5) a rhizobacterium, were symbiotically evaluated for...
In the present study Piriformospora indica (Pi) a phyto-promotional fungus and Azotobacter chroococcumWR5 (AzWR5) a rhizobacterium, were symbiotically evaluated for their role in improving the nutritional quality of wheat (Triticum aestivum L.). Co-inoculation of Pi+AzWR5 modified root system architecture of host and along with increasing the proportion of finer roots by 88% and 92% in C306 and Hd2967 respectively. Furthermore, the synergistic impact of Pi+AzWR5 interplayed for enhanced accumulation of Zn and Fe in different plant parts including grains (3.12 and 1.33 fold respectively). Pi+AzWR5 increased the transfer factor of Zn (62%, 94%, 91% and 213%) and Fe (31%, 54%, 68% and 32%) in root, stem, leaves and grains, respectively, and translocation factor of Zn (20%, 18% and 63%) and Fe (18%, 29% and 29%) for root-stem, root-leaves and root-grains, respectively. In addition to these co-inoculation of endophytes led to several fold increase in expression of four ZIP transporter genes in roots and shoot. In addition to these symbiotic association of endophytes with host led to 3 fold increase in grain yield. We thereby conclude that co-inoculation of Pi+AzWR5 substantially improves mobilization of Zn and Fe from soil and increase its concentration in grains as well as improves crop yield.
Topics: Azotobacter; Basidiomycota; Biofortification; Endophytes; Iron; Plant Roots; Triticum; Zinc
PubMed: 35688099
DOI: 10.1016/j.micres.2022.127075 -
Nature May 1979
Topics: Azotobacter; Cytochromes; Ferritins; Iron; Microscopy, Electron; Spectrum Analysis
PubMed: 450081
DOI: 10.1038/279081a0 -
Journal of General Microbiology Oct 1965
Topics: Azotobacter; DNA, Bacterial; Genetics; In Vitro Techniques; Melanins; Nitrogen Fixation; Pigments, Biological
PubMed: 5883695
DOI: 10.1099/00221287-41-1-1 -
PloS One 2015The genome of the soil-dwelling heterotrophic N2-fixing Gram-negative bacterium Azotobacter chroococcum NCIMB 8003 (ATCC 4412) (Ac-8003) has been determined. It consists...
The genome of the soil-dwelling heterotrophic N2-fixing Gram-negative bacterium Azotobacter chroococcum NCIMB 8003 (ATCC 4412) (Ac-8003) has been determined. It consists of 7 circular replicons totalling 5,192,291 bp comprising a circular chromosome of 4,591,803 bp and six plasmids pAcX50a, b, c, d, e, f of 10,435 bp, 13,852, 62,783, 69,713, 132,724, and 311,724 bp respectively. The chromosome has a G+C content of 66.27% and the six plasmids have G+C contents of 58.1, 55.3, 56.7, 59.2, 61.9, and 62.6% respectively. The methylome has also been determined and 5 methylation motifs have been identified. The genome also contains a very high number of transposase/inactivated transposase genes from at least 12 of the 17 recognised insertion sequence families. The Ac-8003 genome has been compared with that of Azotobacter vinelandii ATCC BAA-1303 (Av-DJ), a derivative of strain O, the only other member of the Azotobacteraceae determined so far which has a single chromosome of 5,365,318 bp and no plasmids. The chromosomes show significant stretches of synteny throughout but also reveal a history of many deletion/insertion events. The Ac-8003 genome encodes 4628 predicted protein-encoding genes of which 568 (12.2%) are plasmid borne. 3048 (65%) of these show > 85% identity to the 5050 protein-encoding genes identified in Av-DJ, and of these 99 are plasmid-borne. The core biosynthetic and metabolic pathways and macromolecular architectures and machineries of these organisms appear largely conserved including genes for CO-dehydrogenase, formate dehydrogenase and a soluble NiFe-hydrogenase. The genetic bases for many of the detailed phenotypic differences reported for these organisms have also been identified. Also many other potential phenotypic differences have been uncovered. Properties endowed by the plasmids are described including the presence of an entire aerobic corrin synthesis pathway in pAcX50f and the presence of genes for retro-conjugation in pAcX50c. All these findings are related to the potentially different environmental niches from which these organisms were isolated and to emerging theories about how microbes contribute to their communities.
Topics: Amino Acid Sequence; Azotobacter; Base Sequence; Biosynthetic Pathways; DNA, Bacterial; Genome, Bacterial; Molecular Sequence Data; Nitrogen Fixation; Sequence Analysis, DNA
PubMed: 26061173
DOI: 10.1371/journal.pone.0127997 -
PloS One 2014Melanins, the ubiquitous hetero-polymer pigments found widely dispersed among various life forms, are usually dark brown/black in colour. Although melanins have variety...
Melanins, the ubiquitous hetero-polymer pigments found widely dispersed among various life forms, are usually dark brown/black in colour. Although melanins have variety of biological functions, including protection against ultraviolet radiation of sunlight and are used in medicine, cosmetics, extraction of melanin from the animal and plant kingdoms is not an easy task. Using complementary physicochemical techniques (i.e. MALDI-TOF, FTIR absorption and cross-polarization magic angle spinning solid-state (13)C NMR), we report here the characterization of melanins extracted from the nitrogen-fixing non-virulent bacterium Azotobacter chroococcum, a safe viable source. Moreover, considering dihydroxyindole moiety as the main constituent, an effort is made to propose the putative molecular structure of the melanin hetero-polymer extracted from the bacterium. Characterization of the melanin obtained from Azotobacter chroococcum would provide an inspiration in extending research activities on these hetero-polymers and their use as protective agent against UV radiation.
Topics: Azotobacter; Melanins; Nitrogen Fixation; Spectrum Analysis
PubMed: 24416247
DOI: 10.1371/journal.pone.0084574 -
Scientific Reports Jul 2020Bacterial alginate initially consists of 1-4-linked β-D-mannuronic acid residues (M) which can be later epimerized to α-L-guluronic acid (G). The family of AlgE...
Bacterial alginate initially consists of 1-4-linked β-D-mannuronic acid residues (M) which can be later epimerized to α-L-guluronic acid (G). The family of AlgE mannuronan C-5-epimerases from Azotobacter vinelandii has been extensively studied, and three genes putatively encoding AlgE-type epimerases have recently been identified in the genome of Azotobacter chroococcum. The three A. chroococcum genes, here designated AcalgE1, AcalgE2 and AcalgE3, were recombinantly expressed in Escherichia coli and the gene products were partially purified. The catalytic activities of the enzymes were stimulated by the addition of calcium ions in vitro. AcAlgE1 displayed epimerase activity and was able to introduce long G-blocks in the alginate substrate, preferentially by attacking M residues next to pre-existing G residues. AcAlgE2 and AcAlgE3 were found to display lyase activities with a substrate preference toward M-alginate. AcAlgE2 solely accepted M residues in the positions - 1 and + 2 relative to the cleavage site, while AcAlgE3 could accept either M or G residues in these two positions. Both AcAlgE2 and AcAlgE3 were bifunctional and could also catalyze epimerization of M to G. Together, we demonstrate that A. chroococcum encodes three different AlgE-like alginate-modifying enzymes and the biotechnological and biological impact of these findings are discussed.
Topics: Alginates; Amino Acid Sequence; Azotobacter; Azotobacter vinelandii; Bacterial Proteins; Biocatalysis; Carbohydrate Epimerases; Genes, Bacterial; Multigene Family; Sequence Alignment; Substrate Specificity
PubMed: 32719381
DOI: 10.1038/s41598-020-68789-3 -
Journal of Biochemistry Apr 1973
Topics: Azotobacter; Cell-Free System; Chromatography, DEAE-Cellulose; Enzyme Activation; Oxidoreductases
PubMed: 4720066
DOI: 10.1093/oxfordjournals.jbchem.a130151 -
Journal of Bacteriology Jan 1970A nitrogenase system that remains in the supernatant fluid after centrifuging for 3 hr at 180,000 x g can be extracted from Azotobacter vinelandii by osmotic lysis of...
A nitrogenase system that remains in the supernatant fluid after centrifuging for 3 hr at 180,000 x g can be extracted from Azotobacter vinelandii by osmotic lysis of the bacteria. This nitrogenase preparation is oxygen-labile and appears to be similar, though not identical, to that obtained from Clostridium pasteurianum. The particulate characteristic and oxygen stability of previously described preparations are likely due to the method of cell disruption, e.g., in the French pressure cell. The data support a nitrogenase model system in the intact cell in which oxygen-labile enzymes are protected from oxygen by the extensive internal membranous system which Azotobacter synthesize only when they fix nitrogen.
Topics: Acetylene; Azotobacter; Cell Membrane; Centrifugation; Microscopy, Electron; NAD; Nitrogen Fixation; Osmosis; Oxidation-Reduction; Oxidoreductases; Oxygen
PubMed: 4312544
DOI: 10.1128/jb.101.1.292-296.1970