Corey Johnson

Anthropogenic compounds such as pesticides, textile dyes, solvents, explosives, and pharmaceuticals can persist in the environment for years and cause toxicity to humans and wildlife. Pentachlorophenol (PCP) is a highly toxic pesticide in use since the 1930s. It is designated as a priority pollutant by the US EPA. Interestingly, environmental microbes have evolved new metabolic pathways for degradation of some of these chemicals. Evolution begins with promiscuous activities of enzymes that normally serve other functions. These enzymes assemble in a patchwork fashion to catalyze the conversion of the pollutants into metabolites that can be utilized by other existing metabolic networks. The bacterium Sphingobium chlorophenolicum, which was isolated from PCP-contaminated sediment, has a newly evolved pathway for the degradation of PCP. The purpose of this study is to elucidate mechanistic details of this pathway. Our focus will be on a tandem of enzymes that enable the process. The proposed questions will be addressed using site directed mutagenesis, kinetic assays, and electron paramagnetic resonance (EPR) spectroscopy. The data obtained will quantitatively demonstrate how the pathway evolved, how highly reactive intermediates in the pathway are sequestered for protection, and how a toxic contaminant can be converted to a nutrient for the bacterium.