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  • 2000-2004  (1)
  • 1990-1994  (4)
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  • 1
    Keywords: Hochschulschrift
    Type of Medium: Online Resource
    Pages: Online-Ressource (129 Seiten = 4 MB) , Illustrationen, Graphen
    Edition: 2021
    Language: German
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  • 2
    Keywords: Hochschulschrift
    Type of Medium: Online Resource
    Pages: Online-Ressource (99 Seiten = 5 MB) , Illustrationen, Graphen, Karten
    Edition: 2021
    Language: German
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  • 3
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Nitrogen is the single most limiting factor for rice production. Detailed knowledge on nitrogen dynamics in rice fields is therefore of major importance for developing sustainable rice production. A combination of state-of-the-art microsensor, stable isotope tracer, and molecular techniques was used to evaluate coupled nitrification–denitrification potentials and community structure of ammonia-oxidizing bacteria in a high yield irrigated rice cropping system in the Philippines, without the use of microcosm incubations. The multiple approaches showed a high degree of concordance among methods and thereby clarified the investigated processes. Numbers and potential activity of ammonia-oxidizing bacteria in the system reflected the availability of substrate in three defined soil factions with a ranking of: surface soil 〉 rhizosphere 〉 bulk soil. No nitrification activity was measured between spit applications of N fertilizer. However, nitrification was induced upon nitrogen amendment in intact soil cores. Despite induction by nitrogen amendment, the loss of nitrogen through coupled nitrification–denitrification was less than 10% of the plant nitrogen uptake. Denaturant gradient gel electrophoresis of amoA fragments revealed no differences in diversity profiles between the soil fractions, and phylogenetic analysis, based on amoA genes retrieved from the rice paddy soil, identified a set of mutually very similar sequences related to Nitrosomonas nitrosa.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-072X
    Keywords: Lipoamino acid ; Glycine lipid ; Ornithine lipid ; Sulfonolipid ; Chemosystematic marker ; Cytophaga spp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cytophaga johnsonae Stanier strain C21 (C. johnsonae C21) contains phosphatidylethanolamine (PE), an unusual glycine-containing lipid (glycine lipid), and two kinds of unidentified lipid as major lipid components. One of the latter lipids was identified by chemical and physicochemical methods as iso-3-hydroxy fatty acid, α-amide linked to ornithine and esterified to iso-nonhydroxy fatty acid (ornithine lipid). The other lipid was identified as a sulfonolipid by a tracer experiment using 35S. PE, glycine lipid and sulfonolipid were found in all seven species of Cytophage examined, namely, C. huchinsonii, C. heparina, C. johnsonae C21, C. aquatilis, and three unidentified species of Cytophaga. However, ornithine lipid was found only in the latter five species. By contrast, a serine-containing lipid, which is a specific lipid component of Flavobacterium species, was not found in any species of Cytophaga examined. The possible use and significance of amino acid-containing lipids and sulfonolipids as chemosystematic markers of the Cytophaga species are discussed.
    Type of Medium: Electronic Resource
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  • 5
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    Unknown
    Wiley
    In:  Environmental Toxicology & Water Quality, 8 (3). pp. 299-311.
    Publication Date: 2018-03-22
    Description: Current measures of microbe‐mediated biogeochemical processes in sediments were examined for their potential use as indicators of heavy metal ecotoxicity in both river sediments and bacterial cultures. Assays were carried out with HgCl2, CuSO4, and 3CdSO4 · 8H2O added to sediment samples and bacterial cell suspensions at concentrations ranging from 0.1 to 10 mM and 0.1 μM to 1 mM, respectively. Chemoautotrophic CO2 fixation by Elbe River sediment microbiota was most sensitive to Hg2+ and Cd2+, but not to Cu2+. Among the estimates of heterotrophic productivity, incorporation of leucine into cellular protein showed clearer dose responses than incorporation of thymidine into bacterial DNA. Thymidine incorporation was highly resistant to and even stimulated by metal ions, particularly in starved and anaerobic cultures of a test strain of Vibrio anguillarum. Similar metal ion induced “overshoot” responses beyond the levels of untreated controls were noted for mineralization of 14C‐glucose by V. anguillarum and, in the case of Cd2+, also in sediment. As a less complex measure of microbial respiratory activity, succinate dehydrogenase (SDH) showed normal dose responses without stimulatory effects, as long as bacterial cell homogenates were assayed. Despite this result, it is concluded that levels of SDH in natural sediment microbiota are inevitably affected by metal‐induced processes of selection and enzyme synthesis, and would thus fail to provide an appropriate measure of metal ecotoxicity. The final conclusion is that current parameters of microbial production and activity often reveal dose responses that do not fulfill basic requirements of ecotoxicity testing in metal‐polluted sediments.
    Type: Article , PeerReviewed
    Format: text
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