Investigating the ecology, activity and interactions of microorganisms bioremediating aquatic ecosystems contaminated with recalcitrant compounds.

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PAHs are natural components of fossil fuels, and are classified as Priority Persistent Pollutants (PPP). In the UK, PAH contamination is widespread in the environment. High molecular weight polycyclic aromatic hydrocarbons (HMW-PAHs) are highly toxic, recalcitrant compounds which can be biomagnified from one trophic level to another, causing significant environmental problems in aquatic ecosystems. In addition to HMW-PAHs, vast quantities of wastewaters are generated (known as tailing pond waters, TPW) during the extraction and processing of super heavy oils. Such process waters contain complex mixtures of highly toxic organic compounds known as naphthenic acids (NAs). NAs are present in TPW in high concentrations (40-120 mg l-1) and are highly toxic to many organisms in the environment including humans, fish and microorganisms (Dokholyan & Magomedov, 1983; Clemente et al., 2004). Currently, contaminated wastewaters are stored in vast ponds until their toxicity is reduced to acceptable levels for incorporation into reclamation schemes. With the volume of process waters expected to reach 1 billion m3 by 2025, there is a significant risk of large-scale environmental pollution during storage. Thus, removing both NAs and HMW-PAHs is important to the environment, society and economy. Although HMW-PAHs and NAs are among the most toxic, recalcitrant organic pollutants found in the environment, they are also among the least studied. Aquatic systems contaminated with NAs and HMW-PAHs pose a severe threat to the environment and human health. As well as the obvious societal and environmental benefits for remediating NAs and HMW-PAHs, the project will provide great economic benefits. Microbial treatment of NAs and HMW-PAHs has clear cost and environmental advantages. The main project output will be the development of cost-effective, rapid bioremediation of severely contaminated aquatic systems. We will develop novel strategies and tools to enhance the biodegradation of NAs and HMW-PAHs from contaminated environments. By increasing in situ biodegradation rates, polluted wastewaters can be detoxified more quickly, accelerating incorporation into reclamation schemes and removing expensive storage costs. This study will enable us to better understand the ecology, diversity and activity of the microbes responsible for the degradation of these recalcitrant, toxic compounds. We will investigate how novel microbial interactions and degradation pathways can be exploited to enhance degradation rates. However, the transformation of HMW-PAHs & NAs is very complex and influenced by a combination of microbial activities and interactions, biogeochemical factors and the physical-chemical properties of the compound. Therefore, it is necessary to adopt a cross-disciplinary approach to investigate the processes at multiple levels, from pure cultures to communities in microcosms and field studies. The main focus will be to identify the key organisms responsible for NA and HMW-PAH biodegradation in aquatic environments. We will investigate the microbial interactions, obtain and optimize degrading pure cultures and consortia, and validate degradation/ detoxification capacity in TPW, other complex wastewaters and contaminated freshwater systems. We will follow the degradation process, metabolite accumulation, toxicity, biosurfactant production and microbial community composition, diversity and activity. We will design gene probes based on molecular analysis of the main microbes found in the environment, new isolates and data from the literature. However, almost nothing is known about the metabolic pathways of NA-degrading microbes (and thus we lack suitable gene probes), and so the student will develop the research at UoE that has begun to elucidate NA catabolic pathways. A key project output is to identify microbes with the ability to degrade NAs and HMW-PAHs in situ and optimise strategies/consortia for increasing biodegradation rates.