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Microbiology (Reading, England) Jun 2011Azotobacter vinelandii is a soil bacterium that undergoes differentiation to form cysts that are resistant to desiccation. Upon induction of cyst formation, the...
Azotobacter vinelandii is a soil bacterium that undergoes differentiation to form cysts that are resistant to desiccation. Upon induction of cyst formation, the bacterium synthesizes alkylresorcinols that are present in cysts but not in vegetative cells. Alternative sigma factors play important roles in differentiation. In A. vinelandii, AlgU (sigma E) is involved in controlling the loss of flagella upon induction of encystment. We investigated the involvement of the sigma factor RpoS in cyst formation in A. vinelandii. We analysed the transcriptional regulation of the rpoS gene by PsrA, the main regulator of rpoS in Pseudomonas species, which are closely related to A. vinelandii. Inactivation of rpoS resulted in the inability to form cysts resistant to desiccation and to produce cyst-specific alkylresorcinols, whereas inactivation of psrA reduced by 50 % both production of alkylresorcinols and formation of cysts resistant to desiccation. Electrophoretic mobility shift assays revealed specific binding of PsrA to the rpoS promoter region and that inactivation of psrA reduced rpoS transcription by 60 %. These results indicate that RpoS and PsrA are involved in regulation of encystment and alkylresorcinol synthesis in A. vinelandii.
Topics: Azotobacter vinelandii; Bacterial Proteins; DNA-Binding Proteins; Desiccation; Electrophoretic Mobility Shift Assay; Gene Expression Regulation, Bacterial; Resorcinols; Sigma Factor; Transcription Factors
PubMed: 21454367
DOI: 10.1099/mic.0.046268-0 -
Scientific Reports Mar 2022Since nitrogenase is irreversibly inactivated within a few minutes after exposure to oxygen, current studies on the heterologous expression of nitrogenase are limited to...
Since nitrogenase is irreversibly inactivated within a few minutes after exposure to oxygen, current studies on the heterologous expression of nitrogenase are limited to anaerobic conditions. This study comprehensively identified genes showing oxygen-concentration-dependent expression only under nitrogen-fixing conditions in Azotobacter vinelandii, an aerobic diazotroph. Among the identified genes, nafU, with an unknown function, was greatly upregulated under aerobic nitrogen-fixing conditions. Through replacement and overexpressing experiments, we suggested that nafU is involved in the maintenance of nitrogenase activity under aerobic nitrogenase activity. Furthermore, heterologous expression of nafU in nitrogenase-producing Escherichia coli increased nitrogenase activity under aerobic conditions by 9.7 times. Further analysis of NafU protein strongly suggested its localization in the inner membrane and raised the possibility that this protein may lower the oxygen concentration inside the cells. These findings provide new insights into the mechanisms for maintaining stable nitrogenase activity under aerobic conditions in A. vinelandii and provide a platform to advance the use of nitrogenase under aerobic conditions.
Topics: Azotobacter; Azotobacter vinelandii; Escherichia coli; Nitrogen; Nitrogen Fixation; Nitrogenase; Oxygen
PubMed: 35264690
DOI: 10.1038/s41598-022-08007-4 -
Journal of Bacteriology Aug 1961Marcus, Leon (University of California, Davis), and Allen G. Marr. Polyol dehydrogenases of Azotobacter agilis. J. Bacteriol. 82:224-232. 1961.-Two soluble...
Marcus, Leon (University of California, Davis), and Allen G. Marr. Polyol dehydrogenases of Azotobacter agilis. J. Bacteriol. 82:224-232. 1961.-Two soluble diphosphopyridine-linked polyol dehydrogenases are formed by Azotobacter agilis (A. vinelandii). The first, d-mannitol dehydrogenase is induced by d-mannitol and all of the pentitols except l-arabitol. Ribitol is an excellent inducer of mannitol dehydrogenase although it is not metabolized, nor does the enzyme act upon it. This allows study of the gratuitous induction of mannitol dehydrogenase. Of the polyols tested, mannitol dehydrogenase oxidizes d-mannitol, d-arabitol, d-rhamnitol, and perseitol, demonstrating its requirement for substrates bearing the d-manno configuration. The corresponding 2-ketoses, d-fructose, d-xylulose, and presumably d-rhamnulose, and perseulose are reduced. The second enzyme, l-iditol dehydrogenase is induced only by polyols containing the d-xylo configuration, i.e., sorbitol and xylitol. l-Iditol dehydrogenase oxidizes d-xylo polyols seven times faster than it does d-ribo polyols. Substrates oxidized include l-iditol, sorbitol, xylitol, and ribitol. The corresponding 2-ketoses, l-sorbose, d-fructose, d-xylulose, and d-ribulose, are reduced. The two polyol dehydrogenases have been separated and purified by chromatography on a modified cellulose ion exchanger.
Topics: Azotobacter; Fructose; L-Iditol 2-Dehydrogenase; Mannitol; Oxidation-Reduction; Oxidoreductases; Pentoses; Ribitol; Sorbitol; Sugar Alcohols
PubMed: 13766585
DOI: 10.1128/jb.82.2.224-232.1961 -
The Journal of Biological Chemistry Jul 1988The crystal structure of the 7Fe ferredoxin from Azotobacter vinelandii has been redetermined using area detector data to 2.7-A resolution and a new derivative....
The crystal structure of the 7Fe ferredoxin from Azotobacter vinelandii has been redetermined using area detector data to 2.7-A resolution and a new derivative. Tetragonal crystals of the protein were maintained at pH 8.0. The results show that the structure previously reported was in error and confirms a recent independent report of the structure (Stout, G.H., Turley, S., Sieker, L. C., and Jensen, L. H. (1988) Proc. Natl. Acad. Sci. U. S. A. 85, in press). The protein fold is similar to the homologous 8Fe ferredoxin structure for the N-terminal half of the protein; the C-terminal residues wrap around this structure. The structure contains a 3Fe cluster coordinated by cysteines 8, 16, and 49 and a 4Fe cluster coordinated by cysteines 20, 39, 42, and 45. However, there are two free sulfhydryls, cysteines 11 and 24, in the new model. Cysteine 24 is in contact with the [4Fe-4S] cluster. Cysteine 11 is shielded from solvent by residues 86-90.
Topics: Azotobacter; Ferredoxins; Iron; Models, Molecular; Protein Conformation; X-Ray Diffraction
PubMed: 3379067
DOI: 10.2210/pdb3fd1/pdb -
Proceedings of the National Academy of... Mar 1965
Topics: Adenine Nucleotides; Adenosine Triphosphate; Azotobacter; Azotobacter vinelandii; Creatine; Creatinine; Electron Transport; Electrons; Enzyme Inhibitors; Nitrogen Fixation; Oxidoreductases; Research; Rhodospirillum; Rhodospirillum rubrum; Sulfites
PubMed: 14338231
DOI: 10.1073/pnas.53.3.532 -
Journal of Bacteriology Dec 1966
Topics: Azotobacter; Hydrolases; Mutation; Nitrogen
PubMed: 5958112
DOI: 10.1128/jb.92.6.1828-1830.1966 -
Journal of Bacteriology Jan 1962Robrish, Stanley A. (University of California, Davis) and Allen G. Marr. Location of enzymes in Azotobacter agilis. J. Bacteriol. 83: 158-168. 1962.-If the cells of...
Robrish, Stanley A. (University of California, Davis) and Allen G. Marr. Location of enzymes in Azotobacter agilis. J. Bacteriol. 83: 158-168. 1962.-If the cells of Azotobacter agilis are disrupted by osmotic shock, respiratory enzymes and the compounds characteristic of cell wall and cytoplasmic membrane are recovered almost completely in large particles. The large particles obtained by osmotic shock were found by electron microscopy to consist of cell wall, cell membrane, and an internal membrane appearing as either vesicles or tubules in section. These envelopes are free of all the soluble cytoplasmic material and are essentially free of ribosomes. Small particles obtained by osmotic shock are ribosomes; small particles obtained by sonic oscillation consist of both ribosomes and amorphous material, presumably fragments of the envelope.
Topics: Azotobacter; Cell Membrane; Cytoplasm; Enzymes; Microscopy, Electron
PubMed: 14492953
DOI: 10.1128/jb.83.1.158-168.1962 -
The Biochemical Journal Oct 1986Flavodoxin in the hydroquinone state acts as an electron donor to nitrogenase in several nitrogen-fixing organisms. The mid-point potentials for the oxidized-semiquinone... (Comparative Study)
Comparative Study
Electron transfer to nitrogenase. Characterization of flavodoxin from Azotobacter chroococcum and comparison of its redox potentials with those of flavodoxins from Azotobacter vinelandii and Klebsiella pneumoniae (nifF-gene product).
Flavodoxin in the hydroquinone state acts as an electron donor to nitrogenase in several nitrogen-fixing organisms. The mid-point potentials for the oxidized-semiquinone and semiquinone-hydroquinone couples of flavodoxins isolated from facultative anaerobe Klebsiella pneumoniae (nifF-gene product, KpFld) and the obligate aerobe Azotobacter chroococcum (AcFld) were determined as a function of pH. The mid-point potentials of the semiquinone-hydroquinone couples of KpFld and AcFld are essentially independent of pH over the range pH 7-9, being -422 mV and -522 mV (normal hydrogen electrode) at pH 7.5 respectively. The mid-point potentials of the quinone-semiquinone couples at pH 7.5 are -200 mV (KpFld) and -133 mV (AcFld) with delta Em/pH of -65 +/- 4 mV (KpFld) and -55 +/- 2 mV (AcFld) over the range pH 7.0-9.5. This indicates that reduction of the quinone is coupled to protonation to yield a neutral semiquinone. The significance of these values with respect to electron transport to nitrogenase is discussed. The amino acid compositions, the N- and C-terminal amino acid sequences and the u.v.-visible spectra of KpFld and AcFld were determined and are compared with published data for flavodoxins isolated from Azotobacter vinelandii.
Topics: Amino Acid Sequence; Amino Acids; Azotobacter; Electron Transport; Flavodoxin; Flavoproteins; Klebsiella pneumoniae; Membrane Potentials; Nitrogenase; Oxidation-Reduction; Spectrophotometry
PubMed: 3541922
DOI: 10.1042/bj2390069 -
Journal of Bacteriology May 1968Poly-beta-hydroxybutyrate (PHB) from various representative strains of the genera Azotobacter, Beijerinckia, and Derxia was isolated and characterized. During growth in...
Poly-beta-hydroxybutyrate (PHB) from various representative strains of the genera Azotobacter, Beijerinckia, and Derxia was isolated and characterized. During growth in shake culture, with glucose as a carbon and energy source, and molecular nitrogen as a nitrogen source, increase in dry weight appeared linear, and PHB formed a constant percentage of the dry weight. In a medium containing 1% (w/v) glucose, PHB declined with the onset of the stationary phase of growth; with 2% (w/v) glucose, an increase in PHB content during stationary phase was noted in the case of some strains, before a subsequent decline. The decrease in PHB as a percentage of dry cellular weight (not of total amount present in the culture) during growth of some strains with 2% as opposed to 1% (w/v) glucose may be ascribed to a greater production of capsular polysaccharide. PHB content could not be used as a taxonomic criterion. Strain differences were as great as or greater than species differences. The only strain of Beijerinckia fluminensis obtained contained PHB, but it could not be grown on the nitrogen-free medium used. Two species of the genus Azotomonas, reported to be aerobic, nonsymbiotic nitrogen-fixers, did not grow on the nitrogen-free medium used and did not produce PHB during growth with a combined nitrogen source.
Topics: Azotobacter; Bacteria; Culture Media; Hydroxybutyrates
PubMed: 5650085
DOI: 10.1128/jb.95.5.1798-1803.1968 -
Polish Journal of Microbiology 2013Effects of pre-sowing soybean seed inoculation with Bradyrhizobium japonicum alone or with mixed inoculants containing soybean rhizobia and Azotobacter chroococcum were...
Effects of pre-sowing soybean seed inoculation with Bradyrhizobium japonicum alone or with mixed inoculants containing soybean rhizobia and Azotobacter chroococcum were compared. In the pot experiment all the tested strains of soybean rhizobia in pure cultures or in mixtures with A. chroococcum significantly improved nodulation of soybean plants and seed yields of this crop. In micro-plot experiments pre-sowing soybean seeds treatment with the inoculant containing the most effective strain 94P of B. japonicum alone or with the mixed inoculant of strain 94P and A. chroococcum were equally effective in improving nodulation intensity and seed yields of soybean in comparison to the uninoculated soybean.
Topics: Azotobacter; Bradyrhizobium; Plant Root Nodulation; Seeds; Soil Microbiology; Glycine max
PubMed: 24730143
DOI: No ID Found