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  • 1
    Electronic Resource
    Electronic Resource
    Nodulation pattern and acetylene reduction (nitrogen fixation) activity of some highland and lowland Acacia species of Ethiopia (1998)
    Springer
    Biology and fertility of soils 27 (1998), S. 60-64 
    Details
    ISSN: 1432-0789
    Keywords: Key words Acacia spp. ; Bradyrhizobium ; Rhizobium ; Nitrogen fixation ; Nitrogen accumulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Endosymbionts from the Ethiopian highland acacia species Acacia abyssinica, A. negrii and A. etbaica, and the lowland species A. nilotica, A. prasinata, A.senegal, A. seyal, A. tortilis and Faidherbia (Acacia) albida were isolated and characterized. Seven tree species were found to be nodulated by species of both Rhizobium and Bradyrhizobium. F. (Acacia) albida and A. senegal were nodulated by only Bradyrhizobium or Rhizobium, respectively. In A. abyssinica, both genera were isolated from the same nodule, whereas in A. nilotica and A. tortilis, both strains were isolated from different nodules of the same plant. The nitrogen fixation (acetylene reduction) activities varied considerably and showed no correlation with the nitrogen content of the plant. Highland species were as effective as lowland plants, thus demonstrating good potential for soil reclamation. The endosymbionts isolated proved rather promiscuous, efficiently nodulating other Acacia spp. and some tropical grain legumes, but did not nodulate temperate legumes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050400
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  • 2
    Electronic Resource
    Electronic Resource
    Nodulation of African yam bean (Sphenostylis stenocarpa) by Bradyrhizobium sp. isolated from Erythrina brucei (1997)
    Springer
    Biology and fertility of soils 25 (1997), S. 209-210 
    Details
    ISSN: 1432-0789
    Keywords: Key wordsBradyrhizobium ; Sphenostylis stenocarpa ; Nitrogen fixation ; Soil reclamation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract African yam bean (Sphenostylis stenocarpa), which is widely cultivated in Africa because of its growth capability on marginal soils, was nodulated by an endosymbiont (characterized and designed Bradyrhizobium sp. AUEB20) isolated from the Ethiopian tree Erythrina brucei with the formation of a small number of large, indeterminate N2-fixing nodules. In contrast, 24 other isolates from Ethiopian woody legumes were ineffective. Strain AUEB20 promiscuously nodulated a number of tropical legumes, but none out of five European crop plants tested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050305
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  • 3
    Electronic Resource
    Electronic Resource
    Physical and chemical properties of the nitrogenase proteins from Azotobacter vinelandii (1974)
    Springer
    Archives of microbiology 98 (1974), S. 93-100 
    Details
    ISSN: 1432-072X
    Keywords: Azotobacter ; Nitrogenase ; Iron Sulfur Proteins ; Properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The purified Mo-Fe protein and Fe protein of nitrogenase from Azotobacter vinelandii have molecular weights (MW) of about 216000 and 64000, respectively. The Mo-Fe protein is composed of subunits of about 56000 MW, and the Fe protein has 2 equivalent subunits of about 33000 MW. The isoelectric point of the Mo-Fe protein is 5.2 and that of the Fe protein is 4.7. Amino acid compositions reflect the acidic nature of the proteins. The Mo-Fe protein yielded 24 atoms of Fe, 20 atoms of acid-labile sulfide and 1.54 atoms of Mo per molecule. Analysis of the Fe protein showed 3.45 atoms of Fe per molecule.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00425272
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  • 4
    Electronic Resource
    Electronic Resource
    Relative levels of guanosine 5′-diphosphate 3′-diphosphate (ppGpp) in some N2 fixing bacteria during derepression and repression of nitrogenase (1981)
    Springer
    Archives of microbiology 128 (1981), S. 341-342 
    Details
    ISSN: 1432-072X
    Keywords: Nitrogen fixation ; Regulation ; Guanosine 5′-diphosphate 3′-diphosphate (ppGpp)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Addition of ammonium to N2 fixing cultures of Azotobacter vinelandii, Klebsiella pneumoniae and Clostridium pasteurianum rapidly reduced the intracellular levels of guanosine 5′-diphosphate 3′-diphosphate (ppGpp) by 70–90%. This change might reflect a regulatory role of ppGpp in nitrogen metabolism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00422542
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  • 5
    Electronic Resource
    Electronic Resource
    Relationships between nitrogenase, glutamine synthetase, glutamine, and energy charge in Azotobacter vinelandii (1981)
    Springer
    Archives of microbiology 128 (1981), S. 412-415 
    Details
    ISSN: 1432-072X
    Keywords: Nitrogenase ; Glutamine synthetase ; Repression ; Amino acid pools ; Adenine nucleotide pools ; Azolobacter vinelandii
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract When continuous cultures of Azotobacter vinelandii were supplied with ammonium or nitrate in amounts, which just repressed nitrogenase synthesis completely, both the intracellular glutamine level and the degree of adenylylation of the glutamine synthetase (GS) increased only slightly (from 0.45–0.50 mM and from 2 to 3 respectively), while the total GS level remained unaffected. Higher amounts of ammonium additionally inhibited the nitrogenase activity, caused a strong rise in the intracellular glutamine concentration and adenylylation of the GS, but caused no change in the ATP/ADP ratio. These results are considered as evidence that in A. vinelandii the regulation of nitrogenase synthesis is not linked to the adenylylation state of the GS and to the intracellular glutamine level, and that the inhibition of the nitrogenase activity as a consequence of a high extracellular ammonium level is not mediated via a change in the energy charge.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00405923
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  • 6
    Electronic Resource
    Electronic Resource
    Quantitative relations for the repression of nitrogenase synthesis in Azotobacter vinelandii by ammonia (1974)
    Springer
    Archives of microbiology 101 (1974), S. 153-159 
    Details
    ISSN: 1432-072X
    Keywords: Azotobacter vinelandii ; Nitrogenase ; Repression ; Ammonia Determination ; Oxygen Effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A method is described which allows the quantitative determination of small ammonia concentrations in the culture of nitrogen-fixing microorganisms. With this method the ammonia concentration range was estimated in which repression of nitrogenase synthesis in Azotobacter vinelandii occurs. Both in batch and continuous cultures there was no repression below 10 μM, whereas nitrogenase synthesis stopped completely if the ammonia concentration in the medium exceeded 25 μM.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00455935
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  • 7
    Electronic Resource
    Electronic Resource
    Ammonium uptake and metabolism by nitrogen fixing bacteria (1976)
    Springer
    Archives of microbiology 111 (1976), S. 85-91 
    Details
    ISSN: 1432-072X
    Keywords: Ammonium metabolism ; Ammonium transport ; Glutamine synthetase ; Nitrogenase ; Glutamate synthase ; Glutamate dehydrogenase ; Nitrate reductase (dissimilatory) ; Klebsiella pneumoniae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The primary steps of N2, ammonia and nitrate metabolism in Klebsiella pneumoniae grown in a continuous culture are regulated by the kind and supply of the nitrogenous compound. Cultures growing on N2 as the only nitrogen source have high activities of nitrogenase, unadenylated glutamine synthetase and glutamate synthase and low levels of glutamate dehydrogenase. If small amounts of ammonium salts are added continuously, initially only part of it is absorbed by the organisms. After 2–3 h complete absorption of ammonia against an ammonium gradient coinciding with an increased growth rate of the bacteria is observed. The change in the extracellular ammonium level is paralleled by the intracellular glutamine concentration which in turn regulates the glutamine synthetase activity. An increase in the degree of adenylation correlates with a repression of nitrogenase synthesis and an induction of glutamate dehydrogenase synthesis. Upon deadenylation these events are reversed.—After addition of nitrate ammonia appears in the medium, probably due to the action of a membrane bound dissimilatory nitrate reductase.—Addition of dinitrophenol causes transient leakage of intracellular ammonium into the medium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00446553
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  • 8
    Electronic Resource
    Electronic Resource
    Pathways and regulation of N2, ammonium and glutamate assimilation by Clostridium formicoaceticum (1983)
    Springer
    Archives of microbiology 134 (1983), S. 167-169 
    Details
    ISSN: 1432-072X
    Keywords: Nitrogenase ; Glutamine synthetase ; Glutamate synthase ; Glutamate dehydrogenase ; Asparagine synthetase ; Alanine dehydrogenase ; β-Methylaspartase ; Clostridium formicoaceticum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Clostridium formicoaceticum possesses the following enzymes for the assimilation of N2 and NH 4 + : nitrogenase, glutamine synthetase, NADH- and NADPH-dependent glutamate synthase, NADH- and NADPH-dependent glutamate dehydrogenase, NADPH-dependent alamine dehydrogenase, and NH 4 + -dependent asparagine synthetase. Nitrogenase and glutamine synthetase are repressed and alanine dehydrogenase is induced by NH 4 + , while the synthesis of the other enzymes is not influenced by the extracellular NH 4 + level. Glutamate is degraded via glutamate mutase and β-methylaspartase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00407953
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  • 9
    Electronic Resource
    Electronic Resource
    Whole cell respiration and nitrogenase activities in Azotobacter vinelandii growing in oxygen controlled continuous culture (1983)
    Springer
    Archives of microbiology 134 (1983), S. 68-72 
    Details
    ISSN: 1432-072X
    Keywords: Azotobacter vinelandii ; Continuous culture ; Oxygen control ; Nitrogen fixation ; Respiratory protection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Azotobacter vinelandii strain OP was grown in continuous culture at various dissolved oxygen concentrations of air (100% air saturation of the medium=225 ±14 μM O2). Sucrose was added as carbon source and either dinitrogen or ammonia as nitrogen sources. Irrespective of the nitrogen source steady state cultures showed the following general responses with dissolved oxygen concentrations increasing from about 1% to 30% air saturation: (i) cell protein levels, (ii) the amount of cell protein formed per sucrose consumed as well as (iii) nitrogenase activity decreased by at least a factor of two while (iv) cellular respiration increased. At higher oxygen concentrations the parameters changed only slightly, if at all. Increasing the sucrose concentration in the inflowing medium (s R) from 3 g/l to 15 g/l increased the total level of cellular respiration with nitrogen-fixing cultures but was more pronounced with ammonium-assimilating cultures. With nitrogen-fixing cultures cell protein levels increased five-fold while the ratio of protein formed per sucrose consumed as well as cellular nitrogenase activity remained unaffected. With ammonium-assimilating cultures the cell protein level was only doubled and the level of cell protein formed per sucrose consumed was decreased at the higher s R. Increasing the dilution rate at a constant oxygen concentration of 45% air saturation resulted in an almost parallel increase of both cellular respiratory and nitrogenase activity at low and moderate dilution rates. At high dilution rates nitrogenase activity increased steeply over the respiratory activity. Nitrogen-fixing cultures adapted to various oxygen concentrations were subjected to oxygen stress by increasing the oxygen concentration for 7 min. In all cases, this resulted in a complete inhibition (‘switch-off’) of nitrogenase activity. Upon restoration of the original oxygen concentration nitrogenase activity returned to a decreased level. The discussion arrives at the conclusion that some of the results are incompatible with the concept of respiratory protection of nitrogenase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00429410
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  • 10
    Electronic Resource
    Electronic Resource
    Ammonium uptake by nitrogen fixing bacteria (1975)
    Springer
    Archives of microbiology 104 (1975), S. 163-169 
    Details
    ISSN: 1432-072X
    Keywords: Azotobacter vinelandii ; Nitrogenase ; Glutamine Synthetase ; Ammonium Pool ; Ammonium Transport ; Citrate Transport ; Repression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Both the changes in the activities of nitrogenase, glutamine synthetase and glutamate dehydrogenase and in the extracellular and intracellular NH4 + concentrations were investigated during the transition from an NH4 + free medium to one containing NH4 + ions for a continuous culture of Azotobacter vinelandii. If added in amounts causing 80–100% repression of nitrogenase, ammonium acetate, lactate and phosphate are absorbed completely, whereas chloride, sulfate and citrate are only taken up to about 80%. After about 1–2 hrs the NH4 + remaining in the medium is absorbed too, indicating the induction or activation of a new NH4 + transport system. One of the new permeases allows the uptake of citrate in the presence of sucrose. Addition of inorganic NH4 + salts leads to acidification of the culture. Anaerobiosis suppresses NH4 + transport. A rise in the extracellular NH4 + level leads to a reversible rise in the glutamine synthetase activity, which is not prevented by chloramphenicol, and to a reversible decrease in nitrogenase activity. During these measurements glutamate dehydrogenase activity remains close to zero. The intracellular NH4 + level of about 0.6 mM does not change when extracellular NH4 + is taken up and repression of nitrogenase starts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00447319
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