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  • 1
    Electronic Resource
    Electronic Resource
    Immunological characterization of nitrogenase in the filamentous non-heterocystous cyanobacterium Oscillatoria limosa (1990)
    Springer
    Planta 182 (1990), S. 287-291 
    Details
    ISSN: 1432-2048
    Keywords: Cyanobacteria ; Fe-protein (immuno-gold localization) ; Nitrogenase ; Nitrogen fixation ; Oscillatoria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The filamentous non-heterocystous cyanobacterium Oscillatoria limosa was subjected to Western blot analyses using two antisera raised against the small subunit (Fe-protein) of the nitrogenase complex. Two polypeptides were recognized in nitrogen-fixing cultures irrespective of the antiserum used while no bands were detectable in nitrate-grown cultures. The apparent molecular weights of the two polypeptides were approximately 40.5 and 39.5 kDa respectively, with the former, probably an inactive form, dominating. In situ immunogold electron microscopy was used to reveal the cellular and subcellular localization on the Fe-protein. All cells of the trichomes of nitrogen-fixing O. limosa showed a dense label. The label was homogeneously distributed throughout the cytoplasm including the thylakoid area. Nitrate-grown cultures contained a very low label.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00197123
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  • 2
    Electronic Resource
    Electronic Resource
    Oxygen protection of nitrogenase in the aerobically nitrogen fixing, non-heterocystous cyanobacterium Oscillatoria sp. (1985)
    Springer
    Archives of microbiology 143 (1985), S. 72-76 
    Details
    ISSN: 1432-072X
    Keywords: Oscillatoria ; Cyanobacteria ; Nitrogen fixation ; Oxygen protection of N2-ase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Oscillatoria sp. strain 23 is a filamentous, non-heterocystous cyanobacterium that fixes nitrogen aerobically. Although, in this organism nitrogenase is inactivated by oxygen a high tolerance is observed. Up to a pO2 of 0.15 atm, oxygen does not have any measurable effects on acetylene reduction. Higher concentrations of oxygen inhibited the activity to a relatively high degree. Evidence for two mechanisms of oxygen protection of nitrogenase in this cyanobacterium was obtained. A high rate of synthesis of nitrogenase may allow the organism to maintain a certain amount of active enzyme under aerobic conditions. Secondly, a switch off/on mechanism may reversibly convert the active enzyme into a non-active form which is insensitive to oxygen inactivation after a sudden and short-term exposure to high oxygen concentrations. It is conceived that these mechanisms in addition to a temporal separation of nitrogen fixation from oxygenic photosynthesis sufficiently explain the regulation process of aerobic nitrogen fixation in this organism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00414771
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  • 3
    Electronic Resource
    Electronic Resource
    Nitrogenase activity in the non-heterocystous cyanobacterium Oscillatoria sp. grown under alternating light-dark cycles (1985)
    Springer
    Archives of microbiology 143 (1985), S. 67-71 
    Details
    ISSN: 1432-072X
    Keywords: Oscillatoria ; Cyanobacteria ; Nitrogen fixation ; Light-dark cycles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The non-heterocystous cyanobacterium Oscillatoria sp. strain 23 fixes nitrogen under aerobic conditions. If nitrate-grown cultures were transferred to a medium free of combined nitrogen, nitrogenase was induced within about 1 day. The acetylene reduction showed a diurnal variation under conditions of continuous light. Maximum rates of acetylene reduction steadily increased during 8 successive days. When grown under alternating light-dark cycles, Oscillatoria sp. fixes nitrogen preferably in the dark period. For dark periods longer than 8 h, nitrogenase activity is only present during the dark period. For dark periods of 8 h and less, however, nitrogenase activity appears before the beginning of the dark period. This is most pronounced in cultures grown in a 20 h light – 4 h dark cycle. In that case, nitrogenase activity appears 3–4 h before the beginning of the dark period. According to the light-dark regime applied, nitrogenase activity was observed during 8–11 h. Oscillatoria sp. grown under 16 h light and 8 h dark cycle, also induced nitrogenase at the usual point of time, when suddenly transferred to conditions of continuous light. The activity appeared exactly at the point of time where the dark period used to begin. No nitrogenase activity was observed when chloramphenicol was added to the cultures 3 h before the onset of the dark period. This observation indicated that for each cycle, de novo nitrogenase synthesis is necessary.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00414770
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  • 4
    Electronic Resource
    Electronic Resource
    Occurrence of nitrogen fixation among Vibrio spp. (1988)
    Springer
    Archives of microbiology 150 (1988), S. 224-229 
    Details
    ISSN: 1432-072X
    Keywords: Vibrio ; V. diazotrophicus ; V. natriegens ; V. pelagius ; V. cincinnatiensis ; Nitrogenase ; Nitrogen fixation ; Oxygen sensitivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Virtually all Vibrio spp. known and available in culture collections and several newly isolated Vibrio sp. were tested for their ability to fix molecular nitrogen, using the acetylene reduction technique, the fixation of the heavy isotope 15N, and by growth on media devoid of combined nitrogen. Among the 27 species tested, four, including V. diazotrophicus, proved to be nitrogenase-positive. The potential of nitrogen fixation was now also discovered in V. natriegens, V. pelagius and V. cincinnatiensis. Among the 9 newly isolated strains, 4 were nitrogenase-positive. These strains were classified as V. diazotrophicus on the basis of DNA homology studies. Nitrogenase was only induced during growth under anaerobic conditions. Dissolved oxygen as low as 1 μM inhibited nitrogenase completely. This inhibition at low oxygen concentration, however, was reversible. 50–100 μM dissolved oxygen inhibited nitrogenase irreversibly.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00407784
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