Toxicity of Polycyclic Aromatic Hydrocarbons Pre- vs. Post-Bioremediation
Date
2020-04-24
Author
Advisors
Gunsch, Claudia
Di Giulio, Richard
Stapleton, Heather
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Abstract
Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental contaminants
implicated in negative human and ecosystem health outcomes, including but not limited
to carcinogenicity and teratogenicity. Bioremediation using PAH-degrading bacteria
and fungi is a noninvasive, relatively low-cost technology capable of reducing environmental
occurrence of PAHs. Employing analytical chemistry methods to detect the extent of
degradation of PAHs, while insightful, is insufficient as the sole determinant of
efficacy of bioremediation. Metabolites created during bacterial degradation of PAHs
can be equally toxic or more toxic than parent compounds. Thus, toxicological assays
of samples undergoing bioremediation are a crucial component for monitoring risk.
The first objective of this project was to develop methods for toxicological assays
that could be employed to determine the efficacy of bioaugmentation strategies currently
being developed with microbial strains isolated from the heavily PAH-contaminated
sediment at the former Republic Creosoting site in the Elizabeth River, VA, USA. The
second objective was to use those methods to test three recently isolated PAH-degrading
bacterial strains to determine their suitability for use in bioaugmentation. Experimental
design included incubation of PAHs with bacteria; extraction of metabolites; analytical
chemistry analysis to determine extent of degradation; then subsequent toxicological
assays of extracted metabolites, including Ames assays to determine mutagenic potency
and zebrafish morphological assays to determine teratogenicity. Four different PAHs
were incubated with three strains of PAH-degrading bacteria in monoculture and co-culture.
Significant degradation of only phenanthrene was observed, accompanied by a slight
increase in mutagenicity and a significant decrease in teratogenicity. Visual inspection
of cultures indicated potential fluoranthene degradation with a concomitant increase
in mutagenic potency in monocultures, but not in co-cultures. Results for teratogenicity
in fluoranthene cultures were inconclusive. Fluoranthene incubation conditions must
be optimized to allow more complete degradation and to achieve more definitive results.
Once optimization is attained, these assays can be employed in future studies to test
additional strains of bacteria as well as fungi that may have capability of degrading
a wider range of PAHs.
Type
Master's projectPermalink
https://hdl.handle.net/10161/20542Citation
deSouza, Beverly (2020). Toxicity of Polycyclic Aromatic Hydrocarbons Pre- vs. Post-Bioremediation. Master's project, Duke University. Retrieved from https://hdl.handle.net/10161/20542.Collections
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