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  • 1
    Electronic Resource
    Electronic Resource
    Immunochemical evidence that nitrogenase is restricted to the heterocysts in Anabaena cylindrica (1984)
    Springer
    Archives of microbiology 137 (1984), S. 194-199 
    Details
    ISSN: 1432-072X
    Keywords: Heterocysts ; Immunoferritin labelling ; Cyanobacteria ; Anabaena ; Nitrogenase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The question of whether the vegetative cells of Anabaena cylindrica synthesize nitrogenase under anaerobic conditions was studied by immunoferritin labelling of the Fe-Mo protein (Component I). Differentiating cultures, incubated under an argon atmosphere, were treated with DCMU 12 h following initiation of induction. DCMU inhibited photosynthetic O2 production, thus insuring strict anaerobic conditions, but had no effect on nitrogenase induction. Fe-Mo protein levels, as determined by rocket immunoelectrophoresis, increased 5-fold within 24h of DCMU treatment. Immunoferritin labelling of aldehyde fixed, ultrathin cryosections of anaerobically induced filaments showed that the Fe-Mo protein was restricted to the heterocyst. Ferritin labelling was shown to be specific by the following criteria: (a) substituting preimmune goat serum for the anti-Fe-Mo protein IgG prevented ferritin labelling; (b) ferritin-conjugated, non-homologous rabbit anti-goat IgG did not bind; (c) incubation of anti-Fe-Mo protein IgG treated sections with rabbit anti-goat IgG prior to the treatment with the ferritin label also prevented labelling. The results provide direct immunochemical evidence that nitrogenase is restricted to the heterocysts even under strictly anaerobic conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00414542
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  • 2
    Electronic Resource
    Electronic Resource
    Oxygen protection of nitrogenase in Frankia sp. HFPArI3 (1984)
    Springer
    Archives of microbiology 139 (1984), S. 162-166 
    Details
    ISSN: 1432-072X
    Keywords: Frankia ; Nitrogenase ; Oxygen protection ; Alnus rubra isolate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract O2 protection of nitrogenase in a cultured Frankia isolate from Alnus rubra (HFPArI3) was studied in vivo. Evidence for a passive gas diffusion barrier in the vesicles was obtained by kinetic analysis of in vivo O2 uptake and acetylene reduction rates in response to substrate concentration. O2 of NH 4 + -grown cells showed an apparent K m O2 of approximately 1μM O2. In N2-fixing cultures a second K m O2 of about 215 μM O2 was observed. Thus, respiration remained unsaturated by O2 at air-saturation levels. In vivo, the apparent K m for acetylene was more than 10-fold greater than reported in vitro values. These data were inter oreted as evidence for a gas diffusion barrier in the vesicles but not vegetative filaments of Frankia sp. HFPArI3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00401993
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  • 3
    Electronic Resource
    Electronic Resource
    Evidence that the barrier to the penetration of oxygen into heterocysts depends upon two layers of the cell envelope (1989)
    Springer
    Archives of microbiology 151 (1989), S. 469-474 
    Details
    ISSN: 1432-072X
    Keywords: Anabaena ; Heterocysts ; Nitrogenase ; Oxygen-protection ; Mutants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mutants of Anabaena sp. PCC 7120 with O2-sensitive acetylene-reducing activity were studied to identify envelope components that contribute to the barrier limiting diffusion of oxygen into the heterocyst. Mutant strain EF114, deficient in a heterocyst-specific glycolipid, reduced acetylene only under strictly anaerobic conditions. Analysis of in vivo O2 uptake as a function of dissolved pO2 showed that EF114 has lost the low affinity, diffusion-limited respiratory component associated with heterocysts in wild-type filaments. The low affinity respiratory activity was also lost in EF116, a mutant in which the cohesiveness of the outer polysaccharide layer was reduced. Restoration of aerobic nitrogen fixation in a spontaneous revertant of EF116 and in a strain complemented with cosmid 41E11 was associated with restoration of the low affinity component of respiratory activity. The results provide evidence that the barrier to diffusion of gas into heterocysts depends upon both the glycolipid layer and the polysaccharide layer of the heterocyst envelope.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00454860
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  • 4
    Electronic Resource
    Electronic Resource
    Growth kinetics and nitrogenase induction inFrankia sp. HFPArI 3 grown in batch culture (1984)
    Springer
    Plant and soil 78 (1984), S. 61-78 
    Details
    ISSN: 1573-5036
    Keywords: Batch culture ; Frankia ; HFPAr13 ; Nitrogenase ; Vesicles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Kinetics of growth and nitrogenase induction inFrankia sp. Ar13 were studied in batch culture. Growth on defined medium with NH 4 + as the N source displayed typical batch culture kinetics; however, a short stationary phase was followed by autolysis. Removal of NH 4 + arrested growth and initiated vesicle differentiation. Vesicle numbers increased linearly and were paralleled by a rise in nitrogenase (acetylene reduction) activity. Nitrogenase activity (10 nM C2H4·mg protein−1·min−1) was sufficient to support growth on N2 and protein levels rose in parallel with nitrogenase induction. Optimal conditions for vesicle and nitrogenase induction were investigated. Maximum rates of acetylene reduction were obtained with 5 to 10 mM K2 HPO4/KH2PO4, 0.1 mM CaCl2 and MgSO4. The optimum pH for acetylene reduction and respiration was around 6.7. The amount (5 to 10 μg protein/ml) and stage (exponential) of growth of the ammonium-grown inoculum strongly influenced the subsequent development of nitrogenase activity. Propionate was the most effective carbon source tested for nitrogenase induction. Respiration in propionate-grown cells was stimulated by CO2 and biotin, suggesting that propionate is metabolized via the propionyl CoA pathway.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02277840
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  • 5
    Electronic Resource
    Electronic Resource
    Culture conditions influencing growth and nitrogen fixation inFrankia sp.HFPCcI3 isolated from Casuarina (1986)
    Springer
    Plant and soil 91 (1986), S. 3-15 
    Details
    ISSN: 1573-5036
    Keywords: Casuarina ; Frankia ; Nitrogenase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The optimum conditions for growth ofFrankia sp. HFPCcI3 isolated fromCasuarina cunninghamiana, were studied in batch culture using defined media. Maximum growth (doubling time was 24 h)_was achieved at 33°C and at pH 6.3 with pyruvate and NH 4 + as the sole C and N sources, respectively. Removal of NH 4 + from the culture medium resulted in vesicle differentiation which was paralleled by induction of acetylene reduction activity. Growth on atmospheric N2 was optimal with combined pyruvate and glucose as the carbon sources and displayed a doubling time of about 48 h. Comparisons in growth and N2-fixing activity ofFrankia strains grown in a variety of cultural conditions demonstrate the range of behavior among the strains.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02181814
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