Characterization of a Mixed Methanotrophic Culture Capable of Chloroethylene Degradation

A consortium of methanotrophs cultured from the St. Joseph’s aquifer in Schoolcraft, MI, was found to exhibit similar methane consumption rates as pure cultures of methanotrophs. The methanotrophic consortium resides within a portion of the aquifer contaminated with a mixed waste plume of per-chloroethylene (PCE) and its reductive dechlorination products from natural attenuation, trichloroeth-ylene (TCE), cis-dichloroethylene (c-DCE), and vinyl chloride (VC). Oxidation kinetics for TCE, c-DCE, and VC were measured for the mixed methanotroph consortium and compared to reported rate parameters for degradation of these chloroethylene compounds by pure methanotrophic cultures. The results demonstrate that the kinetics of chloroethylene oxidation by the Schoolcraft methanotroph population mimic the degradation rates of pure methanotrophic cultures that primarily express par-ticulate methane monooxygenase (pMMO). Molecular and biochemical analyses confirmed that sMMO was not being expressed by these cells. Rather, using competitive reverse transcription-polymerase chain reaction, pmoA, a gene encoding one of the polypeptides of the pMMO was found at a level of (1.57 0.10) 1017 mol pmoA mRNA/g wet soil in soil slurries and (2.65 0.43) 1017 mol pmoA mRNA/l in groundwater. No expression of mmoX, a gene encoding one of the polypeptides of the sMMO, was detected. Key words: methanotroph; trichloroethylene; cis-dichloroethylene; vinyl chloride; reverse transcription-polymerase chain reactio