The treatment of environmental pollution by microorganisms is a promising technology. Various genetic approaches have been developed and used to optimize the enzymes, metabolic pathways and organisms relevant for biodegradation, New information on the metabolic routes and bottlenecks of degradation is still accumulating. enlarging the available toolbox. With molecular methods allowing the characterization of microbial community structure and activities, the performance of microorganisms under in situ conditions and in concert with the indigenous microflora will become predictable.