Date of Award

August 2023

Degree Type


Degree Name

Master of Science


Biological Sciences

First Advisor

John A Berges

Committee Members

Erica B Young, Ryan J Newton, Gyaneshwar Prasad


Polycyclic aromatic hydrocarbons (PAHs) are common pollutants that threaten both ecosystem and human health. The overall objective of my thesis was to describe the effects of prolonged PAH exposure on mixed microbial communities from urban river sediment. My investigation of this objective tested the central hypothesis that the process of culturing bacterial communities with PAH as the sole carbon source significantly affects both community composition and metabolic activity. This research aimed to improve the efficiency of PAH bioremediation by demonstrating the impact of PAH enrichment on the process of obtaining a PAH-degrading consortium. Bioremediation has the potential to reduce the cost, effort, and environmental impact of PAH removal from an impacted environment; streamlining the process of enriching PAH-degrading microbes can make it a more viable strategy in the future. Inoculation of liquid cultures with urban river sediment yielded cultures that could grow with either phenanthrene or pyrene as a sole carbon source. The growth rate, bacterial community composition, and PAH oxidation capacity of these cultures were measured to determine which culture conditions had the greatest effect on these parameters. Growth rate of bacterial cultures was significantly affected by the carbon source immediately present in culture (hereafter carbon source). Overall diversity of the cultures was affected by the riverine sediment collection site (sediment of origin), but the specific bacterial community composition varied with the history of PAH exposure during the duration of the experiment (hereafter culture history). These communities became enriched with known PAH-degrading bacterial taxa such as Pseudomonas, Flavobacterium, and Sphingobium. Oxidation of pyrene (but not phenanthrene) decreased significantly as culture length (measured in days) increased. Culture history and sediment of origin also had significant effects on pyrene oxidation, but these effects may have been exaggerated by outliers and unbalanced experimental design. Overall, this thesis provides a foundation for further analysis of bacterial communities cultured from urban river sediment, comparison between actual and predicted PAH metabolism, and larger-scale bacterial bioremediation trials incorporating environmental conditions and other domains of life.

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