Investigating the role of chemotaxis in the natural source zone depletion of petroleum hydrocarbons
File(s)
Author(s)
Murphy, Cameron William Michael
Type
Thesis
Abstract
Industrial sites contaminated by petroleum hydrocarbons present complex groundwater challenges and environmental risks. Remediation efforts are costly and efficiencies vary over time. Natural source zone depletion (NSZD) involves the gradual degradation of petroleum hydrocarbons through biogeochemical processes. Microbes aid in this degradation, utilising chemotaxis to move towards hydrocarbon sources. This thesis investigates the distribution and interactions of chemotactic and hydrocarbon degrading (CD) microbes through field and laboratory studies. The first study utilised predictive metagenomic profiling (PMP) and ecological analysis to infer functionality and the spatial relationships existing within core samples collected from a legacy site. The second study assessed how microbial communities of varying degrees of chemotactic ability might interact, via the creation of genetically engineered Pseudomonas strains. This ``chemotaxis mutant toolkit'' was used in conjunction with a novel quantitative soft-agar swim fluorescent chemotaxis laser scanning assay to investigate microbial interaction and biomobilisation. The first study found that naphthalene drives the occurrence of CD taxa, including members of the Pseudomonadaceae family. The second study found that a co-culture of chemotactic and non-chemotactic petroleum hydrocarbon degrading Pseudomonas strains has a significantly greater colony perimeter than an equal biomass of non-chemotactic mutants, therefore potentially carrying greater biodegradation potential. This study also found evidence of microbial interaction and biomobilisation of P. putida F1 cheA by P. putida F1 due to variations in the fluorescent intensity profiles producing radial distributions atypical of non-chemotactic bacteria. In conclusion, chemotactic and microbial transport parameters within existing NSZD models should be reviewed to accommodate for CD accumulation in areas of naphthalene contamination. Models should also account for the interactions of chemotactic and non-chemotactic microbes that may occur within the subsurface. Thereby providing a more accurate quantification of risk posed by petroleum hydrocarbon contamination to groundwater as well as providing insight into how to design or manage bioremediation strategy.
Version
Open Access
Date Issued
2023-06
Date Awarded
2024-03
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Butler, Adrian
Stanley, Claire
Lee, Po-Heng
Morgan, Matthew
Puzon, Geoffrey
Sponsor
Commonwealth Scientific and Industrial Research Organization (Australia)
Publisher Department
Civil and Environmental Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)