Hidden Players in Marine Pollution: Investigating Polycyclic Aromatic Hydrocarbon Co-metabolism in Marine Bacteria

Author

Jillian Walton, University of Tennessee, KnoxvilleFollow

Orcid ID

https://orcid.org/0000-0002-1529-9944

Date of Award

5-2025

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Microbiology

Major Professor

Alison Buchan

Committee Members

Jennifer DeBruyn, Todd Reynolds, Andrew Steen

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are toxic, carcinogenic pollutants that are found in nearly every environment. The recalcitrance of these pollutants makes their removal difficult, but microbial degradation has been investigated as a remediation technique. Marine environments are the final destinations for many PAHs, thus investigating marine microbes able to degrade these compounds is crucial to the mitigation of PAH pollution. While investigation into microbial PAH degraders has been conducted, most studies only focus on sole-metabolism, or the degradation of PAHs not dependent the presence of a labile carbon source. The following work investigates another PAH transformation strategy: co-metabolism. Co-metabolism, as defined in this dissertation, is the degradation of PAHs only in the presence of a labile carbon source. Despite coastal PAH pollution co-occurring with high DOC concentrations, little research has investigated co-metabolism, and even less has focused on co-metabolism within marine environments. Here, I show that PAH co-metabolism appears to be a widespread metabolic strategy among marine bacteria, with evidence from both culture collection isolates and environmental isolates. In addition, this co-metabolism appears to proceed by a different mechanism than sole-metabolism due to the lack of PAH degradation genetic biomarkers in strains capable of co-metabolism. The lack of biomarkers may explain the underrepresentation of co-metabolism PAH degraders in literature as many studies only experimentally investigate sole-metabolism and heavily rely on biomarkers to determine PAH degradation activity. Using a model marine bacterium, Ruegeria pomeroyi DSS-3, we found that the mechanism of co-metabolism appears to be carbon source dependent and is likely mediated by non-specific dioxygenases, one of which appears to be common in Roseobacteraceae PAH co-metabolizers. Furthermore, evidence in this dissertation suggests that co-metabolism degraders play an important role in natural attenuation of PAHs within non-chronically polluted environments. This dissertation provides a foundation for future research into PAH co-metabolism by establishing methods and contributing to the known diversity and ecology of marine bacterial PAH co-metabolizers.

Recommended Citation

Walton, Jillian, "Hidden Players in Marine Pollution: Investigating Polycyclic Aromatic Hydrocarbon Co-metabolism in Marine Bacteria. " PhD diss., University of Tennessee, 2025.
https://trace.tennessee.edu/utk_graddiss/12323