MICROBIAL COMMUNITIES ASSOCIATED WITH OIL DEGRADATION IN NIGERIAN SOILS

In this work, we investigated the degradation of crude oil by microbial communities i) in soils from a Nigerian river delta contaminated by oil spills, ii) in mesocosms of a landfarming experiment in Nigeria, and iii) in cultures during laboratory experiments. The microbial biodegradation of hydrocarbons shows great promise to clean oil spills. However, the composition and activities of soil microbial communities are very complex so we believe that it is important to investigate the behaviour of the microbial communities during oil degradation from different perspectives. Chapter 2 is a literature review where we describe the principal genes, enzymes and metabolic pathways that are essential for the aerobic degradation of aliphatic and aromatic hydrocarbons, including the degradation of PAHs. Chapter 3 is a methodological essay where we evaluate the effects of DNA extraction methods and DNA preservation solutions on the quality of microbial community profiling to prevent bias and to improve the preservation and extraction methods. In Chapter 4, we correlate the application of different bioremediation amendments in a large-scale landfarming experiment to oil-removal efficiencies and succession of the community profiles. In Chapter 5, we evaluate a laboratory-based passive-dosing approach in the biodegradation of oil molecules. In Chapter 6, we aimed at correlating the changes of the microbial community to environmental conditions and concentrations of spilt oil during a clean-up project in a Nigerian river delta with mangrove forests. In Chapter 7, we link the degradation of alkanes and PAH to changes in the bacterial community structures to identify key species in oil degradation.