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The EMBO Journal Feb 1986The ntrA, ntrB and ntrC products are responsible for regulating the transcription of many genes involved in the assimilation of poor nitrogen sources in enteric...
The ntrA, ntrB and ntrC products are responsible for regulating the transcription of many genes involved in the assimilation of poor nitrogen sources in enteric bacteria. The presence of a similar system in the non-enteric bacterium Azotobacter vinelandii is reported here. Genes analogous to ntrA and ntrC were isolated from an A. vinelandii gene library by complementation of Escherichia coli mutants. The gene encoding glutamine synthetase, glnA, was also isolated and found to be adjacent to ntrC but distant from ntrA, as it is in enteric organisms. The cloned Azotobacter genes also complemented Klebsiella pneumoniae mutants and hybridized to K. pneumoniae ntrA, ntrC and glnA gene probes. The role of ntrA and ntrC in A. vinelandii was established by using Tn5 insertions in the cloned genes to construct mutants by marker exchange. These mutants show that both ntrA and ntrC are required for the utilization of nitrate as a nitrogen source. However, ntrC is not required for nitrogen fixation by A. vinelandii, in contrast with K. pneumoniae where both ntrA and ntrC are essential.
Topics: Azotobacter; Cloning, Molecular; DNA Restriction Enzymes; Escherichia coli; Genes; Genes, Bacterial; Genetic Complementation Test; Genotype; Glutamate-Ammonia Ligase; Klebsiella pneumoniae; Mutation; Nitrogen; Nitrogenase
PubMed: 2872049
DOI: 10.1002/j.1460-2075.1986.tb04225.x -
Journal of Bacteriology Mar 1976Cells of Azotobacter vinelandii (ATCC 12837) can be transformed by exogenous deoxyribonucleic acid towards the end of exponential growth. Transformation occurs at very...
Cells of Azotobacter vinelandii (ATCC 12837) can be transformed by exogenous deoxyribonucleic acid towards the end of exponential growth. Transformation occurs at very low frequencies when the deoxyribonucleic acid is purified or when the transformation is carried out in liquid medium. Optimal transformation occurs on plates of Burk nitrogen-free glucose medium containing either high phosphate (10 mM) or low calcium (0 to 0.29 mM) content. Higher levels of calcium are inhibitory, whereas magnesium ions are essential for transformation and growth. Extracellular polymer and capsule are increasingly inhibitory to transformation and are most abundant when the calcium content of the medium is high. Transformation is optimal at pH 7.0 to 7.1 and at 30 C, conditions which also coincide with minimal extracellular polymer production. Nonencapsulated strains are excellent transformation recipients. Glycine-induced pleomorphism reduces the transformation frequency and the degree of inhibition is dependent on the phosphate concentration of the medium. Rifampin resistance and shifts from adenine, hypoxanthine, uracil, and nitrogenase auxotrophy to prototrophy can be achieved. Although single marker transfer is always greater than double marker transfer, the data suggest that rifampin resistance is linked to hypoxanthine, adenine and uracil protorophy at intervals of increasing distance. Rifampin resistance did not appear to be linked to nitrogenase.
Topics: Adenine; Azotobacter; Calcium; Drug Resistance, Microbial; Glucose; Hydrogen-Ion Concentration; Hypoxanthines; Magnesium; Mutation; Nitrogenase; Phosphates; Rifampin; Temperature; Transformation, Genetic; Uracil
PubMed: 3492
DOI: 10.1128/jb.125.3.1080-1087.1976 -
Journal of Bacteriology Feb 1967Escherichia coli and Azotobacter agilis were grown in minimal media until a steady state was established. The distribution of cell size was determined electronically....
Escherichia coli and Azotobacter agilis were grown in minimal media until a steady state was established. The distribution of cell size was determined electronically. From the equation of Collins and Richmond, the growth rate of individual cells was computed as a function of size. The main features of the growth of individual E. coli and A. agilis cells revealed by this work were: the specific growth rate decreased at the time of division, and both the absolute and specific growth rates increased between divisions. The frequency function of interdivision times was computed and was found to be positively skewed with a coefficient of variation of approximately 0.3. The results supported the hypothesis of Koch and Schaechter that the size of an individual cell at division is highly regulated.
Topics: Azotobacter; Cell Division; Escherichia coli; Kinetics; Mathematics; Spectrophotometry
PubMed: 5335966
DOI: 10.1128/jb.93.2.605-617.1967 -
Microbial Biotechnology Jul 2009The enzyme quinoprotein glucose dehydrogenase (GDH) catalyses the oxidation of glucose to gluconic acid by direct oxidation in the periplasmic space of several...
The enzyme quinoprotein glucose dehydrogenase (GDH) catalyses the oxidation of glucose to gluconic acid by direct oxidation in the periplasmic space of several Gram-negative bacteria. Acidification of the external environment with the release of gluconic acid contributes to the solubilization of the inorganic phosphate by biofertilizer strains of the phosphate-solubilizing bacteria. Glucose dehydrogenase (gcd) gene from Escherichia coli, and Azotobacter-specific glutamine synthetase (glnA) and phosphate transport system (pts) promoters were isolated using sequence-specific primers in a PCR-based approach. Escherichia coli gcd, cloned under the control of glnA and pts promoters, was mobilized into Azotobacter vinelandii AvOP and expressed. Sorghum seeds were bacterized with the transgenic azotobacters and raised in earthen pots in green house. The transgenic azotobacters, expressing E. coli gcd, showed improved biofertilizer potential in terms of mineral phosphate solubilization and plant growth-promoting activity with a small reduction in nitrogen fixation ability.
Topics: Azotobacter vinelandii; Cloning, Molecular; Escherichia coli; Gene Expression; Glucose 1-Dehydrogenase; Inorganic Chemicals; Phosphates; Promoter Regions, Genetic; Recombinant Proteins; Seedlings; Sorghum
PubMed: 21255283
DOI: 10.1111/j.1751-7915.2009.00119.x -
The Biochemical Journal Aug 1972Azotobacter beijerinckii was grown in ammonia-free glucose-mineral salts media in batch culture and in chemostat cultures limited by the supply of glucose, oxygen or...
Azotobacter beijerinckii was grown in ammonia-free glucose-mineral salts media in batch culture and in chemostat cultures limited by the supply of glucose, oxygen or molecular nitrogen. In batch culture poly-beta-hydroxybutyrate was formed towards the end of exponential growth and accumulated to about 74% of the cell dry weight. In chemostat cultures little poly-beta-hydroxybutyrate accumulated in organisms that were nitrogen-limited, but when oxygen limited a much increased yield of cells per mol of glucose was observed, and the organisms contained up to 50% of their dry weight of poly-beta-hydroxybutyrate. In carbon-limited cultures (D, the dilution rate,=0.035-0.240h(-1)), the growth yield ranged from 13.1 to 19.8g/mol of glucose and the poly-beta-hydroxybutyrate content did not exceed 3.0% of the dry weight. In oxygen-limited cultures (D=0.049-0.252h(-1)) the growth yield ranged from 48.4 to 70.1g/mol of glucose and the poly-beta-hydroxybutyrate content was between 19.6 and 44.6% of dry weight. In nitrogen-limited cultures (D=0.053-0.255h(-1)) the growth yield ranged from 7.45 to 19.9g/mol of glucose and the poly-beta-hydroxybutyrate content was less than 1.5% of dry weight. The sudden imposition of oxygen limitation on a nitrogen-limited chemostat culture produced a rapid increase in poly-beta-hydroxybutyrate content and cell yield. Determinations on chemostat cultures revealed that during oxygen-limited steady states (D=0.1h(-1)) the oxygen uptake decreased to 100mul h(-1) per mg dry wt. compared with 675 for a glucose-limited culture (D=0.1h(-1)). Nitrogen-limited cultures had CO(2) production values in situ ranging from 660 to 1055mul h(-1) per mg dry wt. at growth rates of 0.053-0.234h(-1) and carbon-limited cultures exhibited a variation of CO(2) production between 185 and 1328mul h(-1) per mg dry wt. at growth rates between 0.035 and 0.240h(-1). These findings are discussed in relation to poly-beta-hydroxybutyrate formation, growth efficiency and growth yield during growth on glucose. We suggest that poly-beta-hydroxybutyrate is produced in response to oxygen limitation and represents not only a store of carbon and energy but also an electron sink into which excess of reducing power can be channelled.
Topics: Anaerobiosis; Azotobacter; Carbon Dioxide; Culture Media; Glucose; Hydroxybutyrates; Nitrogen; Oxygen Consumption
PubMed: 4643700
DOI: 10.1042/bj1281193 -
TSitologiia I Genetika 2014Strains of Azotobacter mediate in the nitrogen fixation process by reducing of N2 to ammonia. In this study, 50 strains were isolated from different rhizospheric soil in...
Strains of Azotobacter mediate in the nitrogen fixation process by reducing of N2 to ammonia. In this study, 50 strains were isolated from different rhizospheric soil in central Iran, by using soil paste-plate method. These strains were biochemically identified and characterized on differential LG medium based on morphological and physiological properties. Results obtained showed that identified strains were belonging to three species, namely A. chroococcum, A. vinelandii and A. beijernckii. In order to molecular analysis, the 16S rRNA gene was amplified using 27f and 1495r primers and PCR products were subsequently digested with RsaI, HpaII and HhaI. Cluster analysis based on amplified ribosomal DNA restriction analysis were revealed intraspecific polymorphism and differentiated strains into two mains clusters, clusters A and B. Cluster A strains were related to the A. vinelandii, whereas cluster B strains were related to the A. chroococcum and A. beijerinckii. The results show that amplified ribosomal DNA restriction analysis is a powerful and discriminatory tool for the identification of members of the genus Azotobacter.
Topics: Azotobacter; DNA Restriction Enzymes; DNA, Bacterial; DNA, Ribosomal; Genes, Bacterial; Genetic Variation; Multigene Family; Phylogeny; Polymorphism, Restriction Fragment Length; RNA, Bacterial; RNA, Ribosomal, 16S; Sequence Analysis, DNA; Soil Microbiology
PubMed: 25318174
DOI: No ID Found -
PloS One 2016In Inner Mongolia, steppe grasslands face desertification or degradation because of human overuse and abandonment after inappropriate agricultural management. The soils...
In Inner Mongolia, steppe grasslands face desertification or degradation because of human overuse and abandonment after inappropriate agricultural management. The soils in these abandoned croplands exist in heterogeneous environments characterized by widely fluctuating microbial growth. Quantitative polymerase chain reaction analysis of microbial genes encoding proteins involved in the nitrogen cycle was used to study Azotobacter species, nitrifiers, and denitrifiers in the soils from steppe grasslands and croplands abandoned for 2, 6, and 26 years. Except for nitrifying archaea and nitrous oxide-reducing bacteria, the relative genotypic abundance of microbial communities involved in nitrogen metabolism differed by approximately 2- to 10-fold between abandoned cropland and steppe grassland soils. Although nitrogen-cycle gene abundances varied with abandonment time, the abundance patterns of nitrogen-cycle genes separated distinctly into abandoned cropland versus light-grazing steppe grassland, despite the lack of any cultivation for over a quarter-century. Plant biomass and plant diversity exerted a significant effect on the abundance of microbial communities that mediate the nitrogen cycle (P < 0.002 and P < 0.03, respectively). The present study elucidates the ecology of bacteria that mediate the nitrogen cycle in recently abandoned croplands.
Topics: Azotobacter; Crops, Agricultural; Environment; Nitrogen Cycle; Real-Time Polymerase Chain Reaction; Soil; Soil Microbiology
PubMed: 27140199
DOI: 10.1371/journal.pone.0154697 -
Journal of Microbiology and... Apr 2013Azotobacter vinelandii, a strict aerobic nitrogen-fixing bacterium, has been extensively studied with regard to the ability of N2-fixation due to its high expression of...
Azotobacter vinelandii, a strict aerobic nitrogen-fixing bacterium, has been extensively studied with regard to the ability of N2-fixation due to its high expression of nitrogenase and fast growth. Because nitrogenase can also reduce cyanide to ammonia and methane, cyanide degradation by A. vinelandii has been studied for the application in the bioremediation of cyanide-contaminated wastewater. Cyanide degradation by A. vinelandii in NFS (nitrogen-free sucrose) medium was examined in terms of cell growth and cyanide reduction, and the results were applied for cyanide-contaminated cassava mill wastewater. From the NFS medium study in the 300 ml flask, it was found that A. vinelandii in the early stationary growth phase could reduce cyanide more rapidly than the cells in the exponential growth phase, and 84.4% of cyanide was degraded in 66 h incubation upon addition of 3.0 mM of NaCN. The resting cells of A. vinelandii could also reduce cyanide concentration by 90.4% with 3.0 mM of NaCN in the large-scale (3 L) fermentation with the same incubation time. Finally, the optimized conditions were applied to the cassava mill wastewater bioremediation, and A. vinelandii was able to reduce the cyanide concentration by 69.7% after 66 h in the cassava mill wastewater containing 4.0 mM of NaCN in the 3 L fermenter. Related to cyanide degradation in the cassava mill wastewater, nitrogenase was the responsible enzyme, which was confirmed by methane production. These findings would be helpful to design a practical bioremediation system for the treatment of cyanide-contaminated wastewater.
Topics: Azotobacter vinelandii; Biodegradation, Environmental; Culture Media; Cyanides; Methane; Nitrogenase; Oxidation-Reduction; Wastewater; Water Pollutants, Chemical
PubMed: 23568214
DOI: 10.4014/jmb.1209.09026 -
European Journal of Biochemistry Feb 1986The flavodoxins from Azotobacter vinelandii cells grown N2-fixing and from cells grown on NH4OAc have been purified and characterized. The purified flavodoxins from...
The flavodoxins from Azotobacter vinelandii cells grown N2-fixing and from cells grown on NH4OAc have been purified and characterized. The purified flavodoxins from these cells are a mixture of three different flavodoxins (Fld I, II, III) with different primary structures. The three proteins were separated by fast protein liquid chromatography; Fld I eluted at 0.38 M KCl, Fld II at 0.43 M KCl and Fld III at 0.45 M KCl. The most striking difference between the three flavodoxins was the midpoint potential (pH 7.0, 25 degrees C) of the semiquinone/hydroquinone couple, which was -320 mV for Fld I and -500 mV for the other two flavodoxins (Fld II and Fld III). All three flavodoxins were present in cells grown on NH4OAc. In cells grown on N2 as N source only Fld I and Fld II were found. The concentration of Fld II was 10-fold higher in N2-fixing cells than in cells grown on NH4OAc. Evidence has been obtained that Fld II is involved in electron transport to nitrogenase. As will be discussed, our observation that preparations of Azotobacter flavodoxin are heterogeneous, has consequences for the published data.
Topics: Azotobacter; Chemical Precipitation; Cross Reactions; Electrophoresis, Polyacrylamide Gel; Flavodoxin; Flavoproteins; Immunochemistry; Isoelectric Point; Magnetic Resonance Spectroscopy; Peptide Fragments; Protein Denaturation; Spectrophotometry
PubMed: 3948879
DOI: 10.1111/j.1432-1033.1986.tb09455.x -
Proceedings of the National Academy of... Mar 1964
Topics: Aldehydes; Azotobacter; Azotobacter vinelandii; Benzaldehydes; Benzoates; Benzoquinones; Carbon Isotopes; Chromatography; Hydroxybenzoates; Kidney; Metabolism; Pharmacology; Rats; Research; Saccharomyces; Saccharomyces cerevisiae; Tyrosine; Ubiquinone
PubMed: 14171457
DOI: 10.1073/pnas.51.3.444