Characterization of Reductive Dehalogenases in a Chlorinated Ethene-Degrading Bioaugmentation Culture

Perchloroethene and trichloroethene are among the most persistent groundwater pollutants, and Dehalococcoides is the only known species that can degrade these compounds completely to non-toxic ethene. Characterization of the reductive dehalogenase (RDase) enzymes responsible for dechlorination is important to understanding this process. A series of dechlorination assays were performed with whole cell suspensions and cell-free extracts of three Dehalococcoides-containing mixed microbial consortia to compare dechlorination kinetics and to characterize co-contaminant inhibition. Michaelis-Menten kinetic parameters Vmax and Km, as well as non-competitive inhibition coefficients for 1,1,1-trichloroethane and 1,1-dichloroethane inhibitors are reported. Secondly, blue native gel electrophoresis was developed as a method to isolate active protein complexes containing RDases. Thirdly, sources of variability in the isotopic fractionation of vinyl chloride to ethene reaction step were examined using cell-free extracts and whole-cell suspensions. Understanding the function and range of RDases are goals towards the successful application of Dehalococcoides-containing cultures to remediate contaminated sites.