Studies on bacterial activities during degradation of mineral oil compounds

Morasch, Barbara

Studies on bacterial activities during degradation of mineral oil compounds

Dateien

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Datum

2003

Autor:innen

Morasch, Barbara

URI (zitierfähiger Link)

http://nbn-resolving.de/urn:nbn:de:bsz:352-opus-12682

Link zur Lizenz

Urheberrechtlich geschützt

Open Access-Veröffentlichung

Open Access Green

Sammlungen

Biologie

Titel in einer weiteren Sprache

Untersuchungen zur bakteriellen Aktivität im Zuge des Abbaus von Mineralölkomponenten

Publikationstyp

Dissertation

Publikationsstatus

Published

Zusammenfassung

Adsorber resin Amberlite-XAD7 was applied in bacterial batch cultures to enrich, isolate, and cultivate bacteria that use putatively toxic substrates.
2. Strain OX39, isolated from contaminated aquifer material in the presence of XAD7, is an endospore-forming sulfate-reducing bacterium. Its substrate range was found to be limited to toluene, m- and, o-xylene, as well as their degradation products benzoic acid, m-, and o-toluic acid. Degradation to CO2 proceeds via fumarate addition to one methyl group. Analysis of its 16S rRNA gene showed that strain OX39 is the first aromatic hydrocarbon-using member of the genus Desulfotomaculum.
3. For measurement of 2H/1H isotope fractionation upon bacterial toluene degradation, an alternative approach by gas chromatographic analysis was developed. Selectively deuterium labeled toluene species were supplied as growth substrates. Results acquired could be validated using IRM-GC-MS.
4. Carbon and hydrogen isotope fractionation during toluene degradation were found to be independent of growth temperatures under sulfate-reducing conditions. In contrast, during aerobic toluene degradation by P. putida strain mt-2, isotope fractionation was found to vary with growth temperatures. Isotope fractionation was not influenced by degradation rates.
5. Isotope enrichment factors for toluene determined in growth experiments with bacterial pure cultures taking nitrate, Fe(III), or sulfate as electron acceptors were close to each other. Significantly higher isotope enrichment was observed under oxic conditions. Therefore, important prerequisites for quantification of contaminant degradation in situ might be fulfilled only in absence of O2.
6. The main process leading to isotope fractionation during toluene degradation was the first enzyme reaction, whereas substrate diffusion to the cells and substrate uptake by the bacteria was negligible. Influence of additional masses by deuterium labels was not detectable.
7. Various bacteria degrading different substrates in enzyme reactions of the glycyl radical type caused isotope enrichment in a narrow range. An average enrichment factor may be applicable to quantify overall biodegradation of contaminants degraded via this pathway in the environment.
8. Aerobic degradation of different methyl benzenes via a methyl monooxygenase reaction was accompanied by large isotope enrichment effects. Mono- and dioxygenase reactions attacking the aromatic ring led to characteristically weak or insignificant hydrogen and carbon isotope fractionation. The big differences preclude quantitative applications in oxic environments. However, isotope shifts are positive indications for in situ biodegradation.

Zusammenfassung in einer weiteren Sprache

Zur Anreicherung, Isolierung und Kultivierung von Bakterien, die potentiell toxische Substrate verwerten, wurde den Kulturflaschen das Adsorberharz Amberlite-XAD7 zugesetzt.
2. Stamm OX39, isoliert aus kontaminiertem Boden in Gegenwart von XAD7, ist ein endosporenbildender Sulfatreduzierer. Die einzigen Wachstumssubstrate waren Toluol, m-Xylol, o-Xylol, sowie deren Abbauprodukte Benzoesäure, m- und o-Tolylsäure. Der Abbau beginnt mit einer Addition von Fumarat an die Methylgruppe und verläuft vollständig bis zu CO2. Laut Analyse des 16S rRNA-Gens ist Stamm OX39 das erste Bakterium, das dem Genus Desulfotomaculum angehört und aromatische Kohlenwasserstoffe verwerten kann.
3. Zur Messung der 2H/1H Isotopenfraktionierung im Zuge des bakteriellen Toluolabbaus wurde ein auf Gaschromatographie basierendes Verfahren entwickelt. Spezifisch deuteriummarkierte Toluolspezies dienten dabei als Wachstumssubstrate. Die Ergebnisse wurden mittels IRM-GC-MS überprüft.
4. Die Kohlenstoff- und Wasserstoffisotopenfraktionierung beim Toluolabbau war unter sulfatreduzierenden Bedingungen unabhängig von der Wachstumstemperatur. Im Gegensatz dazu variierte die Isotopenfraktionierung beim aeroben Toluolabbau von P. putida Stamm mt-2 mit der Wachstumstemperatur. Die Isotopenfraktionierung war unabhängig von den Abbauraten.
5. Isotopen-Anreicherungsfaktoren beim Toluolabbau verschiedener Bakterienstämme, die Nitrat, Fe(III) oder Sulfat als Elektronenakzeptoren verwendeten, waren miteinander vergleichbar. Deutlich höhere Anreicherungsfaktoren ergaben sich für den aeroben Toluolabbau mit P. putida Stamm mt-2. Die Abwesenheit von O2 ist somit eine Voraussetzung für die Quantifizierung des Schadstoffabbaus in der Umwelt mittels Isotopenanalyse.
6. Die erste Enzymreaktion war der wichtigste Prozess, der zu einer Isotopenfraktionierung beim Toluolabbau führte. Die Diffusion des Substrats zur Zelle sowie die Substrataufnahme in die Zelle waren bezüglich ihrer Fraktionierung vernachlässigbar. Masseneffekte der zusätzlichen Deuteriumatome waren nicht nachweisbar.
7. Bakterienstämme, die unterschiedliche Substrate in Glycylradikal-katalysierten Enzymreaktionen abbauten, verursachten Isotopenanreicherungsfaktoren in einem engen Bereich. Eine Gesamtquantifizierung aller Schadstoffe, die in der Umwelt über diesen Abbauweg umgesetzt werden, wäre mit einem durchschnittlichen Anreicherungsfaktor für diesen Reaktionstyp denkbar.
8. Beim aeroben Abbau von Methylbenzolen bewirkte die Methylmonooxygenase-Reaktion deutliche Isotopenanreicherungseffekte. Mono- bzw. Dioxygenasen, die am aromatischen Ring angreifen, führten zu schwachen bis nicht-signifikanten Isotopeneffekten. Diese deutlichen, mechanistisch bedingten Unterschiede schließen eine Quantifizierung in situ aus. Jedoch kann eine Verschiebung in der Isotopenzusammensetzung als Hinweis für Bioabbau gelten.

Fachgebiet (DDC)

570 Biowissenschaften, Biologie

Schlagwörter

mikrobielle Isotopenfraktionierung, Schadstoffabbau, Benzylsuccinatsynthase, Glycylradikal, microbial isotope fractionation, groundwater contaminants, benzylsuccinate synthase, glycyl radical, natural attenuation

Zitieren

ISO 690

MORASCH, Barbara, 2003. Studies on bacterial activities during degradation of mineral oil compounds [Dissertation]. Konstanz: University of Konstanz

BibTex

@phdthesis{Morasch2003Studi-7690,
  year={2003},
  title={Studies on bacterial activities during degradation of mineral oil compounds},
  author={Morasch, Barbara},
  address={Konstanz},
  school={Universität Konstanz}
}

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Prüfungsdatum der Dissertation

December 16, 2003