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  • 1995-1999  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Nitrification, denitrification and growth in artificial Thiosphaera pantotropha biofilms as measured with a combined microsensor for oxygen and nitrous oxide (1995)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 17 (1995), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract: Cells of the aerobic denitrifier and heterotrophic nitrifier Thiosphaera pantotropha and of the traditional denitrifier Paracoccus denitrificans were immobilized in a 1.5 mm thick agar layer (biofilm) and submersed in liquid medium. A combined microsensor for O2 and N2O was used to record microprofiles of these two species in biofilms where the reduction of N2O was inhibited by acetylene. Nitrification in T. pantotropha was not affected by the addition of acetylene and by using a diffusion-reaction model to simulate the N2O profiles it was possible to calculate depth profiles of both nitrification and denitrification. The validity of the calculations when both nitrification and denitrification were operating in concert was confirmed by performing identical calculations on data obtained for a P. denitrificans biofilm. At high NO3− concentrations, part of the NO3− reduced by T. pantotropha biofilms was reduced only to NO2− and N2O production thus did not reflect total NO3− reduction. When NO2− and no NO3− was present in the water above the biofilm N2O production was recorded in the anoxic zone directly below the oxic zone. Nitrous oxide production was never detected in the oxic zone of the biofilms, although aerobic denitrification was described for the original isolate of this bacterium. The growth rate of T. pantotropha in the oxic region of the biofilms was estimated to be 0.42 h−1 which is slightly higher than rates previously obtained in liquid culture. In the T. pantotropha biofilms nitrification was calculated to account for more than 50% of the O2 consumption whereas this process only consumed about 10% of the O2 in liquid culture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6941.1995.tb00137.x
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Confirmation of ‘aerobic denitrification’ in batch cultures, using gas chromatography and 15N mass spectrometry (1995)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 18 (1995), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract: Because of a revival in the controversy surrounding ‘aerobic denitrification’, especially in relation to Thiosphaera pantotropha, activity in aerobic batch cultures was evaluated using gas chromatography and mass spectrometry after the addition of 15N-labelled NH4+ and NO2−. Aerobic denitrifying activity in T. pantotropha was present, but only at about 10% of the originally-reported levels. The activity of ‘Pseudomonas denitrificans’ was similar to previously-reported values. Alcaligenes faecalis showed significant aerobic denitrifying activity, producing almost equivalent amounts of N2 and N2O. An unidentified pseudomonad, isolate G4, presumably requires anoxia for enzyme activity as it did not denitrify aerobically, even though it has a constitutive denitrifying pathway.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6941.1995.tb00168.x
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Macrophyte development and resuspension regulate the photosynthesis and production of benthic microalgae (1997)
    Springer
    Hydrobiologia 350 (1997), S. 1-11 
    Details
    ISSN: 1573-5117
    Keywords: resuspension ; benthic microalgae ; submergedmacrophytes ; light competition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of macrophyte growth on microbenthicphotosynthetic activity was studied in two largeenclosures situated in a shallow, eutrophic lake.Macrophytes were allowed to develop stands of 100%coverage in one enclosure whereas they were harvestedat emergence in the other. Although less than 10% ofthe incident light reached the benthic microphytesbelow the macrophytes at mid-summer, when themacrophytes reached their maximum coverage, theseasonal productivity (April–October) of themicrobenthic community was still 355 g C m−2corresponding to 65% of the productivity in theenclosure without macrophytes. Although the lightattenuation by the macrophytes had a strong negativeeffect on microbenthic photosynthesis, the negativeeffect was partly balanced by increased watertransparency caused by increased grazing on thephytoplankton, and the shelter provided by the plantsalso resulted in less resuspension. Analysis withmicrosensors for oxygen and scalar irradiance showedthat the capacity for photosynthesis was evenlydistributed throughout the uppermost 3 mm of thesediment and in the approximately 3-mm flocculent layercovering the sediment. Microbenthic photosynthesisseemed primarily limited by light. The microsensoranalysis also demonstrated how conventional oxygenexchange experiments underestimate the truephotosynthetic rates and indicated that more realisticrates might be obtained by measuring oxygen exchangeif the exchange is facilitated by vigorousstirring.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003052226202
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    Paper (German National Licenses)
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