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  • 1
    ISSN: 1432-072X
    Keywords: Campylobacter ; Interspecies hydrogen transfer ; Fumarate reduction ; Nitrate reduction ; Thiosulphate reduction ; Sulphur reduction ; Knallgas reaction ; Hydrogen oxidation ; Formate oxidation ; Sulphide production ; Clostridium cochlearium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A free-living aspartate-fermenting Campylobacter spec. was shown to utilize hydrogen produced in mixed culture by Clostridium cochlearium from glutamate. Resting cells of Campylobacter were shown to reduce aspartate, fumarate and malate as well as nitrate, nitrite, hydroxylamine, sulphite, thiosulphate and elemental sulphur with molecular hydrogen. Growth of Campylobacter spec. was demonstrated with formate as electron donor and nitrate, thiosulphate, elemental sulphur or oxygen as electron acceptor in the presence of acetate as carbon source.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-072X
    Keywords: Photosynthesis ; Respiration ; Nitrogenase ; Light-dark-cycle ; Oxygen-protection ; Cyanobacteria ; Oscillatoria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract When growing in laternating light-dark cycles, nitrogenase activity (acetylene reduction) in the filamentous, non-heterocystous cyanobacterium Oscillatoria sp. strain 23 (Oldenburg) is predominantly present during the dark period. Dark respiration followed the same pattern as nitrogenase. Maximum activities of nitrogenase and respiration appeared at the same time and were 3.6 μmol C2H4 and 1.4 mg O2 mg Chl a -1·h-1, respectively. Cultures, adapted to light-dark cycles, but transferred to continuous light, retained their reciprocal rhythm of oxygenic photosynthesis and nitrogen fixation. Moreover, even in the light, oxygen uptake was observed at the same rate as in the dark. Oxygen uptake and nitrogenase activity coincided. However, nitrogenase activity in the light was 6 times as high (22 μmol C2H4 mg Chl a -1·h-1) as compared to the dark activity. Although some overlap was observed in which both oxygen evolution and nitrogenase activity occurred simultaneously, it was concluded that in Oscillatoria nitrogen fixation and photosynthesis are separated temporary. If present, light covered the energy demand of nitrogenase and respiration very probably fulfilled a protective function.
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  • 3
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The nitrogenase activity in the cyanobacterial mat of a laminated microbial ecosystem was investigated by the acetylene reduction method. Measurements under several conditions such as light and dark, aerobic and anaerobic and by inhibiting photosystem II by 10-5 M DCMU showed the nitrogenase activity to be light stimulated and to some degree inhibited by oxygen. An appreciable amount of activity was also present under complete aerobic conditions. We estimated 8 to 15 kg N fixed per hectare per year for that part of the intertidal flat supporting growth of cyanobacteria. By measuring a vertical sediment profile, nitrogenase was shown to be associated with the cyanobacterial mat. Diurnal measurements of nitrogenase showed two activity peaks, one at sunrise and one at sunset. Following population dynamics in the cyanobacterial mat showed Microcoleus sp., Oscillatoria spp., Spirulina sp., Gloeocapsa sp. and sometimes Merismopedia sp. to be present. During four years of observations we never found any heterocystous cyanobacteria. Non-heterocystous cyanobacteria apparently play an important role in nitrogen fixation in this marine intertidal environment.
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