Biphasic nitrogenase activity in Azospirillum brasilense in long lasting batch cultures

1980 ◽  
Vol 128 (2) ◽  
pp. 209-214 ◽  
Author(s):  
Hans Papen ◽  
Dietrich Werner
Keyword(s):  
Azospirillum Brasilense ◽  
Nitrogenase Activity ◽  
Batch Cultures

Effect of hydrogen and oxygen on uptake-hydrogenase activity in nitrogen-fixing and ammonium-grown Azospirillum brasilense

1983 ◽  
Vol 29 (9) ◽  
pp. 1119-1125 ◽  
Author(s):  
Karl H. Tibelius ◽  
Roger Knowles
Keyword(s):  
Azospirillum Brasilense ◽  
Nitrogenase Activity ◽  
Hydrogen Uptake ◽  
Rapid Decline ◽  
Hydrogenase Activity ◽  
Uptake Hydrogenase ◽  
Batch Cultures ◽  
Whole Cells ◽  
Irreversible Inhibition ◽  
Microaerobic Conditions

Hydrogen uptake by Azospirillum brasilense was studied in N2-fixing and NH4Cl-grown batch cultures. The Km for H2 of uptake hydrogenase (O2-dependent H3H uptake) in whole cells was 9 µM. In N2-flxing or NH4Cl-grown cultures hydrogenase activity reached its maximum in late log phase, followed by a rapid decline in stationary phase. In cultures sparged with H2, hydrogenase activity was markedly prolonged. Rates of O2-dependent H3H uptake and H2 uptake measured by gas chromatography were very similar. Hydrogenase derepression required microaerobic conditions, was independent of nitrogenase derepression, did not require exogenous H2, and may be enhanced by electron-donor limitation. Air caused irreversible inhibition of hydrogenase activity. In N-free cultures, theO2 optima for H2 uptake, ranging from 0.5 to 1.25% O2 depending on the phase of growth, were significantly higher than those for nitrogenase activity (C2H2 reduction), 0.15 to 0.35%, suggesting that H2 uptake may have a limited ability to aid in the protection of nitrogenase against inactivation by O2.

Hydrogen metabolism of Azospirillum brasilense in nitrogen-free medium

1980 ◽  
Vol 26 (9) ◽  
pp. 1126-1131 ◽  
Author(s):  
Y. K. Chan ◽  
L. M. Nelson ◽  
R. Knowles
Keyword(s):  
Gas Phase ◽  
Cyclic Gmp ◽  
Azospirillum Brasilense ◽  
Nitrogenase Activity ◽  
Hydrogenase Activity ◽  
Similar Response ◽  
Uptake Hydrogenase ◽  
Hydrogen Metabolism ◽  
Free Medium ◽  
Batch Cultures

Production of H2 by Azospirillum brasilense under N2-fixing conditions was studied in continuous and batch cultures. Net H2 production was consistently observed only when the gas phase contained CO. Nitrogenase activity (C2H2 reduction) and H2 evolution (in the presence of 5% CO) showed a similar response to O2 and were highest at 0.75% dissolved O2. Uptake hydrogenase activity, ranging from 0.3 to 2.5 μmol H2/mg protein per hour was observed in batch cultures under N2. Such rates were more than sufficient to recycle nitrogenase-produced H2. Tritium-exchange assay showed that H2 uptake was higher under Ar than under N2. Uptake hydrogenase was strongly inhibited by CO and C2H2. Cyclic GMP inhibited both nitrogenase and uptake hydrogenase activities.

How Does the DraG-PIIComplex Regulate Nitrogenase Activity in Azospirillum brasilense?

2015 ◽  
pp. 139-146 ◽  
Author(s):  
Xiao-Dan Li ◽  
Fritz K. Winkler ◽  
Luciano F. Huergo
Keyword(s):  
Azospirillum Brasilense ◽  
Nitrogenase Activity

Isolation and genetic analysis of Azospirillum brasilense Nif− mutants

1983 ◽  
Vol 29 (8) ◽  
pp. 968-972 ◽  
Author(s):  
P. Jara ◽  
B. Quiviger ◽  
P. Laurent ◽  
C. Elmerich
Keyword(s):  
Genetic Analysis ◽  
Host Range ◽  
Azospirillum Brasilense ◽  
Nitrogenase Activity ◽  
Plasmid Vector ◽  
Ecori Fragment ◽  
Broad Host Range ◽  
Broad Host Range Plasmid ◽  
Ethylmethane Sulfonate ◽  
Derivatives Of

After ethylmethane sulfonate mutagenesis of Azospirillum brasilense strain 7000, mutants devoid of nitrogenase activity were isolated. Partial diploids were constructed by introducing plasmids pAB35 and pAB36 into the Nif− mutants. The two plasmids were derivatives of the broad host-range plasmid vector pRK290. Plasmid pAB35 contained a 6.7 kilobase pairs (kb) EcoRI fragment which carried the nifHDK gene cluster cloned from strain 7000. Plasmid pAB36 contained the same fragment from which a 2.6-kb PstI fragment that likely covers nifK, and a part of nifD was deleted. The restoration of a Nif+ phenotype by pAB35, but not by pAB36, was observed in the case of mutant 7571, which might be impaired in a structural gene for the nitrogenase complex.

Studies on associative nitrogen fixation by antibiotic-resistant mutants ofAzospirillum brasilensewith genotypes of lentil (Lens culinaris)Rhizobiumstrains in calcareous soil

1985 ◽  
Vol 104 (1) ◽  
pp. 207-215 ◽  
Author(s):  
R. Rai
Keyword(s):  
Nitrogen Fixation ◽  
Azospirillum Brasilense ◽  
Calcareous Soil ◽  
Lens Culinaris ◽  
Nitrogenase Activity ◽  
Dry Weight ◽  
Antibiotic Resistant ◽  
Uninoculated Control ◽  
Resistant Mutants ◽  
Antibiotic Resistant Mutants

SummaryNitrosoguanidine-induced mutation frequencies for resistance to streptomycin, spectinomycin, erythromycin and novomycin were studied inAzospirillum brasilense.Lentil inoculated withA. brasilenseand its mutants andRhizobiumstrains produced increased nodule dry weight, nitrogenase activity of nodules and roots and grain yield compared with an uninoculated control.

scholarly journals Superoxide dismutase, catalase, and peroxidase in ammonium-grown and nitrogen-fixing Azospirillum brasilense

1984 ◽  
Vol 30 (10) ◽  
pp. 1222-1228 ◽  
Author(s):  
Richard W. Clara ◽  
Roger Knowles
Keyword(s):  
Superoxide Dismutase ◽  
Electron Acceptor ◽  
Azospirillum Brasilense ◽  
Polyacrylamide Gel Electrophoresis ◽  
Growth Conditions ◽  
Sod Activity ◽  
Batch Cultures ◽  
Physiological Conditions ◽  
Azospirillum Brasilense Sp7 ◽  
In Cells

Superoxide dismutase (SOD), catalase (CAT), and peroxidase (PER) activities were studied in ammonium-grown and N2-fixing batch cultures of Azospirillum brasilense Sp7. PER activity, as measured using o-dianisidine or 3,3′-diaminobenzidine as the H donor, was not significant in most growth conditions. SOD activity increased in response to higher O2 concentrations but was also present in cells grown anaerobically with nitrate [Formula: see text] or nitrous oxide (N2O) as electron acceptor. CAT activity increased at lower O2 concentrations and was highest in cells grown anaerobically with [Formula: see text] as electron acceptor. Polyacrylamide gel electrophoresis of cell-free extracts revealed only one band of SOD activity under each of the physiological conditions employed, compared with three for aerobically grown Escherichia coli K12. This band proved to be iron-containing SOD (FeSOD) on the basis of inhibitor sensitivity.

Pectin decomposition and associated nitrogen fixation by mixed cultures of Azospirillum and Bacillus species

1992 ◽  
Vol 38 (8) ◽  
pp. 794-797 ◽  
Author(s):  
K. M. Khammas ◽  
P. Kaiser
Keyword(s):  
Nitrogen Fixation ◽  
Azospirillum Brasilense ◽  
Nitrogenase Activity ◽  
Bacillus Species ◽  
Azospirillum Lipoferum ◽  
Pectin Degradation ◽  
Efficient Utilization ◽  
Fermentation Products ◽  
Pure Cultures ◽  
Azospirillum Amazonense

Cocultures of different Azospirillum species with Bacillus polymyxa or Bacillus subtilis allow the efficient utilization of pectin as carbon and energy sources for nitrogen fixation. The nitrogenase activity obtained with cocultures was as high as 30–80 nmol C2H4 h−1 mL−1, a much higher value than that obtained with pure cultures of either Azospirillum (up to 13 nmol C2H4 h−1 mL−1) or B. polymyxa (up to 2 nmol C2H4 h−1 mL−1) alone. To establish to what extent each partner contributed to nitrogenase activity, acetylene reduction was assayed as a function of time and it was also measured on Azospirillum cultivated in the cultures filtrates of the Bacillus. The results suggested that the nitrogenase activity was mostly produced by Azospirillum. The nitrogenase activity occurred at the expense of the degradation and fermentation products of the pectin. The new pectinolytic species, Azospirillum irakense, utilized both degradation and fermentation products of pectin, whereas the nonpectinolytic strains (Azospirillum brasilense, Azospirillum lipoferum, Azospirillum amazonense) utilized only the fermentation products of pectin, including acetic and succinic acids. These cocultures can be considered as metabolic associations, where the Bacillus produces degradation and fermentation products of pectin, which can be used by Azospirillum species. Key words: cocultures, nitrogen fixation, pectin degradation, Azospirillum, Bacillus, metabolic association.

Production of the reserve material poly-β-hydroxybutyrate and its function in Azospirillum brasilense Cd

1985 ◽  
Vol 31 (7) ◽  
pp. 608-613 ◽  
Author(s):  
Sara Tal ◽  
Yaacov Okon
Keyword(s):  
Batch Culture ◽  
Azospirillum Brasilense ◽  
Chemostat Culture ◽  
Nitrogenase Activity ◽  
Dry Weight ◽  
Stress Factors ◽  
Atmospheric Nitrogen ◽  
Mineral Salts ◽  
Reserve Material ◽  
Starvation Conditions

Azospirillum brasilense Cd was grown in ammonium–malate mineral salts medium in batch culture and in chemostat continuous culture. It was found that poly-β-hydroxybutyrate synthesis was favored under oxygen limitation in chemostat culture and under high C/N ratios towards the end of exponential growth in batch culture. The degradation and synthesis of poly-β-hydroxybutyrate under starvation conditions occurred in a biphasic pattern and was affected by the poly-β-hydroxybutyrate content of the cells. During a 7-day incubation period in phosphate buffer, the survival and respiration rate of bacteria containing about 40% poly-β-hydroxybutyrate (dry weight) were higher than those of cells containing about 5% poly-β-hydroxybutyrate. Polymer-rich cells fixed atmospheric nitrogen in the absence of exogenous carbon and combined nitrogen. Biphasic nitrogenase activity was observed during starvation. When nitrogenase activity was high, hydroxybutyrate dehydrogenase activity was low and vice versa. Aerotactic response was higher in polymer-rich cells. In the presence of stress factors such as ultraviolet irradiation, dessication, and osmotic pressure poly-β-hydroxybutyrate-poor cells died more rapidly than poly-β-hydroxybutyrate-rich cells.

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