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dc.contributor.advisor Stapleton, Heather en_US
dc.contributor.advisor Schuler, Andrew J en_US
dc.contributor.author Cooper, Ellen M. en_US
dc.date.accessioned 2009-05-01T18:31:43Z
dc.date.available 2009-05-01T18:31:43Z
dc.date.issued 2009 en_US
dc.identifier.uri http://hdl.handle.net/10161/1154
dc.description Dissertation en_US
dc.description.abstract <p>Dibenzothiophene (DBT) is a constituent of creosote and petroleum waste contamination, it is a model compound for more complex thiophenes, and its degradation by mixed microbial communities has received little attention. The chemical characteristics, environmental fate and ecotoxicology of DBT degradation products are not well understood. This research investigated DBT degradation in an enrichment culture derived from creosote-contaminated estuarian sediment using a suite of assays to monitor bacterial populations, bacterial growth, degradation products, DBT loss, and toxicity. Ultraviolet (UV) irradiation was evaluated as a sequential treatment following biodegradation. Additionally, to advance SYBR-Green qPCR methodology for characterizing mixed microbial communities, an alternative approach for evaluating qPCR data using a sigmoidal model to fit the amplification curve was compared to the conventional approach in artificial mixed communities. The overall objective of this research was to gain a comprehensive understanding of the degradation of a model heterocyclic PAH, DBT, by a mixed microbial community, particularly within the context of remediation goals.</p><p>DBT biodegradation was evaluated in laboratory scale cultures with and without pH control. The microbial community was monitored with 10 primer sets using SYBR-Green quantitative polymerase chain reaction (qPCR). Twenty-seven degradation products were identified by gas chromatography and mass spectrometry (GC/MS). The diversity of these products indicated that multiple pathways functioned in the community. DBT degradation appeared inhibited under acidic conditions. Toxicity to bioluminescent bacteria <italic>Vibrio fischeri</italic> more than doubled in the first few days of degradation, was never reduced below initial levels, and was attributed in part to one or more degradation products. UV treatment following biodegradation was explored using a monochromatic (254 nm) low-pressure UV lamp. While DBT was not extensively photooxidized, several biodegradation products were susceptible to UV treatment. At higher doses, UV treatment following DBT biodegradation exacerbated cardiac defects in <italic>Fundulus heteroclitus</italic> embryos, but slightly reduced toxicity to <italic>V. fischeri</italic>.</p><p>This research provides a uniquely comprehensive view of the DBT degradation process, identifying bacterial populations previously unassociated with PAH biodegradation, as well as potentially hazardous products that may form during biodegradation. Additionally, this research contributes to development of unconventional remediation strategies combining microbial degradation with subsequent UV treatment.</p> en_US
dc.format.extent 5161465 bytes
dc.format.mimetype application/pdf
dc.language.iso en_US
dc.subject Environmental Sciences en_US
dc.subject biodegradation en_US
dc.subject dibenzothiophene en_US
dc.subject polycyclic aromatic hydrocarbon en_US
dc.title Biodegradation of a Sulfur-Containing PAH, Dibenzothiophene, by a Mixed Bacterial Community en_US
dc.type Dissertation en_US
dc.department Environment en_US
duke.embargo.months 12 en_US
dc.date.accessible 2010-05-18T05:00:22Z

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