Genetic bioaugmentation of soil microbial communities for the bioremediation of terephthalic acid

Abstract

The global production of terephthalic acid (TPA), a key precursor in plastic manufacturing, is substantial, and its untreated release into the environment poses ecological risks. This thesis addresses these concerns by developing a genetic bioaugmentation strategy to enhance microbial TPA biodegradation using an engineered conjugative plasmid, pQBR57, carrying a TPA degradation operon (tphKAB). Pseudomonas putida KT2440 (pQBR57-tphKAB) effectively degrades TPA in both liquid media and soil microcosms, and the plasmid’s horizontal transfer to Pseudomonas fluorescens SBW25 facilitates the spread of this bioremediation capability within soil environments. Screening a diverse soil bacterial library demonstrated plasmid host range was largely confined to Pseudomonas, influenced by donor strain identity. Using synthetic soil microbial communities of increasing complexity, experimental evolution showed improved plasmid persistence, transfer, and TPA degradation with pQBR57-tphKAB, which also provided protection against mercury stress, illustrating multifunctionality. Adaptation experiments revealed rapid evolution of P. putida KT2440 for enhanced TPA utilization, driven by the interplay of mutational supply and selection pressure, with genomic analyses identifying key mutations associated with improved degradation. This work advances understanding of plasmid-host dynamics, horizontal gene transfer, and adaptive evolution, providing a genetic bioaugmentation framework for enhancing biodegradation of TPA in environmental and industrial contexts.

Date of Award	16 Dec 2025
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Neil Dixon (Main Supervisor)