Bioremediation, the enhancement of microbial activity to degrade environmental pollutants within aquifers, show great promise to reduce health risks associated with groundwater contamination. The success of bioremediation, however, can be limited by the availability of electron acceptors (e.g. O2) and by the expression of appropriate catabolic enzymes (e.g. toluene dioxygenase). The dissolved oxygen concentration threshold for the expression of toluene dioxygenase, and the ability of various target contaminants and other substrate to induce this enzyme will be investigated. Toluene dioxygenase is an ideal enzyme for a study of bioremediation because of its ability to catalyze the aerobic biotransformation of a wide variety of ubiquitous priority pollutants, including petroleum hydrocarbons (e.g. benzene, toluene, and xylenes) and solvents (e.g. trichlorethylene). Enzyme expression will be quantified using an enzyme linked immuno sorbent assay (ELISA). This project will enhance understanding of the limitations of catabolic enzyme expression during bioremediation. The identification of non-polluting enzyme inducers could also lead to improved bioremediation of trace pollutants and to the development of better cometabolic processes.