Browsing by Subject "PAH"
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Item Unknown Alterations of Endophytic Microbial Community Function in Spartina alterniflora as a Result of Crude Oil Exposure(2021) Addis, SamanthaThe 2010 Deepwater Horizon disaster remains one of the largest oil spills in history. This event caused significant damage to coastal ecosystems, the full extent of which has yet to be fully determined. Crude oil contains both toxic substances that are detrimental to microbes and compounds that may be used as food and energy resources by some microbial species. As a result, oil spills have the potential to cause significant shifts in microbial communities. In this study, we assessed the impact of oil contamination on the function of endophytic microbial communities associated with saltmarsh cordgrass (Spartina alterniflora). Soil samples were collected from two locations in coastal Louisiana, USA: one severely affected by contamination from the Deepwater Horizon oil spill and one relatively unaffected location. Spartina alterniflora seedlings were grown in both soil samples under greenhouse conditions, and GeoChip 5.0 was used to evaluate the endophytic microbial metatranscriptome shifts in response to host oil exposure. Microbial functional shifts were detected in functional categories related to metal homeostasis, organic remediation, and phosphorus utilization. These findings show that host oil exposure elicits multiple changes in metabolic response from their endophytic microbial communities, producing effects that may have the potential to impact host plant fitness.
Item Open Access Plastic Dominates Developmental Toxicity Responses to Burn pit related Smoke in Zebrafish: Role for Polycyclic Aromatic Hydrocarbons(2023-04-27) Smoot, JacobCombustion of mixed materials during open air burning of refuse or housefires produces emissions that worsen air quality and may cause adverse health effects. Although previous studies have linked air pollution exposure from other sources to congenital defects, the potential developmental toxicity of mixed material combustion emissions remains uncertain. The purpose of this study was to compare the developmental toxicity of smoke derived from the combustion of 5 different material types (plywood, cardboard, plastic, mixture, and mixture plus diesel) in zebrafish larvae, a model often used to assess the behavioral and developmental effects of chemicals. Zebrafish have been shown to have similar physiological and biochemical responses to smoke exposure as other vertebrates and absorb chemicals (such as PAHs) through their epidermis from their surroundings. Larvae were exposed to organic extracts of each smoke at various concentrations and assessed for morphological and behavioral toxicity at 5 days post fertilization. All extracts caused concentration-dependent effects, including mortality, impaired swim bladder inflation, pericardial edema, spinal curvature tail kinks, or craniofacial deformities, although plastic and the mixture caused the most pronounced effects. Plastic also altered locomotor responsiveness to light changes to the greatest extent. Interestingly, some morphological and behavioral responses correlated strongly with total and specific polycyclic aromatic hydrocarbons concentrations in the smoke extracts. Overall, the findings suggest that material type and combustion chemistry impact the severity of developmental toxicity of mixed material smoke in zebrafish.Item Open Access Toxicity of Polycyclic Aromatic Hydrocarbons Pre- vs. Post-Bioremediation(2020-04-24) deSouza, BeverlyPolycyclic 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.