Characterization of a Mixed Methanotrophic Culture Capable of Chloroethylene Degradation

Abstract

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 perchloroethylene (PCE) and its reductive dechlorination products from natural attenuation, trichloroethylene (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 particulate methane monooxygenase (pMMO). Molecular and biochemical analyses confirmed that sMMO was not being expressed by these cells. Rather, using competitive reverse transcriptionpolymerase chain reaction, pmoA, a gene encoding one of the polypeptides of the pMMO was found at a level of (1.57 Ϯ 0.10) ϫ 10 Ϫ17 mol pmoA mRNA/g wet soil in soil slurries and (2.65 Ϯ 0.43) ϫ 10 Ϫ17 mol pmoA mRNA/l in groundwater. No expression of mmoX, a gene encoding one of the polypeptides of the sMMO, was detected.

Conceptualizing functional traits and ecological characteristics of methane‐oxidizing bacteria as life strategies

“…sMMO‐expressing cells are able to oxidize a wide range of compounds including aliphatic and aromatic hydrocarbons, and their halogenated derivatives (Burrows et al ., ; Trotsenko and Murrell, ). Similarly, pMMO‐expressing cells, albeit possessing a narrower substrate range (pMMO oxidizes alkanes and alkenes up to C 5 ; Trotsenko and Murrell, ), have been found to degrade mixed pollutants in the laboratory as well as in‐situ (Forrester et al ., ; Lee et al ., ; Paszczynski et al ., ), and even out‐perform sMMO‐expressing cells under specific conditions in the laboratory (Lee et al ., ). Hence, both pMMO‐ and/or sMMO‐expressing cells are applicable for bioremediation.…”

Methanotrophs and copper

“…Using competitive RT‐PCR assays developed in our laboratories (Han & Semrau, 2004), we found that methanotrophic cultures in soil slurries and groundwater from a mixed chloroethane/chloroethene plume expressed only pMMO, and not sMMO, and concluded that pMMO‐expressing cells were responsible for the observed chlorinated hydrocarbon degradation at this site (Forrester et al , 2005).…”

Small-scale oxygen distribution determines the vinyl chloride biodegradation pathway in surficial sediments of riverbed hyporheic zones

“…Cometabolic aerobic degradation is a fortuitous conversion with no clear benefit to the responsible organisms and requires a primary substrate to support microbial growth and energy conservation (Alvarez‐Cohen & Speitel, ). The well‐described cometabolic CAH degradation by methanotrophs (Alvarez‐Cohen & Speitel, ; Forrester et al ., ; Shukla et al ., ) is of interest in hyporheic zones because it can be hypothesized that their activity in upper oxic sediment layers is sustained by methane produced by indigenous methanogens in lower anaerobic layers (Fig. S1).…”