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Title: Role of microbial adaptation in the biodegradation of chemical pollutants : extrapolation from laboratory to rivers
Author: Kowalczyk, Agnieszka
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2013
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The Organisation for Economic Cooperation and Development (OECD) established standardized tests to predict the chemical behaviour in the environment. Difficulties exist in the extrapolation of data from laboratory OECD tests into the environment, and prediction of possible scenarios regarding environmental pollution is not accurate. The current project aimed to increase the realism of OECD tests and to investigate the microbial populations involved in the biodegradation of paranitrophenol (PNP). River water, sediment and biofilms were sampled from a stretch of River Dene with an effluent discharge point (Wellesbourne WWTP), and were used as microbial inocula in biodegradation studies. The effect of light, PNP concentration and inoculum preparation on PNP biodegradation was determined. Culture dependent techniques were used for isolation of PNP-degrading bacteria while culture independent techniques; including 16S rRNA Terminal Restriction Fragment Length Polymorphism, QPCR, and high throughput sequencing targeting the PNP functional genes (pnpA and mar), enabled detection and characterization of PNP-degrading bacteria. Light incubation lead to increased river water pH which inhibited PNP degradation. A threshold PNP concentration was determined around 42 μg/L. Application of biofilm inocula improved the reproducibility of PNP biodegradation at a concentration of 2 mg/L, and increased the amount of microbial biomass in test systems. Pseudomonas syringae was identified as a key PNPdegrader. Additional groups of PNP-degrading bacteria were detected based on the analysis of pnpA and mar functional markers. It was shown that location of sampling site for inoculum collection had no impact on biodegradation test outcome but variation of microbial inocula between sampling dates may affect the biodegradation of PNP. Core and satellite taxa analysis demonstrated that ‘biodegradation lottery’ is not the major process which determines the successful chemical biodegradation, and that probably microbial interactions within inoculum affect proliferation of PNPdegraders, and therefore impact on test results. This project revealed the lack of consideration of microbial inocula in the OECD biodegradation test guidelines. Further experimental work was suggested to expand current studies to different chemicals and rivers, and to develop more predictable approaches for better chemical risk management by Industry and Regulatory bodies.
Supervisor: Not available Sponsor: Unilever (Firm)
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QH301 Biology ; QP Physiology