ARTICLE Biodegradation of Trichloroethene by Methane Oxidizers Naturally Associated with Wetland Plant Roots Christina L. Powell & Abinash Agrawal Received: 9 July 2010 / Accepted: 6 December 2010 # Society of Wetland Scientists 2011 Abstract Trichloroethene (TCE) can undergo natural attenuation within wetland environments, particularly by oxidative processes that occur in the vegetated subsur- face. The goal of this study was to evaluate TCE degradation potential through aerobic cometabolism by methane-oxidizing microorganisms associated with the roots of wetland plant species, Carex comosa and Scirpus atrovirens. The degradation experiments were conducted in 2.4 L Teflon microcosms with 15 g of washed, soil-free roots and amended with methane (2.1 mg/L), oxygen (8 mg/L), and TCE (three enrichment cycles without TCE and four cycles at 150 μg/L, one cycle at 600 μg/L, and one cycle at 900 μg/L of TCE). Our results indicated that methane-oxidizing activity and TCE degradation potential were comparable for the plant species investigated. The initial rates of methane degradation with TCE amendments varied between 0.21 and 0.30 mg L –1 d –1 for Carex comosa, and between 0.14 and 0.25 mg L –1 d –1 for Scirpus atrovirens. The average TCE mass removal per cycle varied between 24 and 32%, and the overall transforma- tion yield was 0.0004 mmol TCE/mmol CH 4 for both plant species. This study suggests that wetland plants can play an important role in the natural attenuation of TCE in contaminated aquatic environments. Keywords Carex comosa . Scirpus atrovirens . TCE . Cometabolism Introduction Trichloroethene (TCE) is a common groundwater contam- inant that poses a threat to human health as a suspected carcinogen (ATSDR 1997). However, TCE can be naturally attenuated in the environment through aerobic and anaer- obic microbial degradation processes. In particular, TCE biodegradation by cometabolic oxidative pathways can lead to its mineralization, facilitated by aerobic microorganisms that utilize a wide range of growth substrates such as methane (Fogel et al. 1986; Little et al. 1988), toluene (Shim et al. 2001), phenol (Chen et al. 2004), ammonia (Kocamemi and Cecen 2007), and several others. Methane as a growth substrate has been successfully studied in a number of systems using both mixed (Fogel et al. 1986) and pure cultures (Little et al. 1988). During cometabolic degradation of TCE with methane, the methane-oxidizing bacteria (methanotrophs) produce a non-specific enzyme, methane monooxygenase (MMO), which oxidizes methane as its substrate and can also fortuitously degrade TCE (Sullivan et al. 1998). In this process, TCE degradation may be initiated as an epoxidation reaction catalyzed by the MMO, with NADH as an immediate energy source (Chang and Alvarez-Cohen 1995). Microbial methane production (methanogenesis) is ubiq- uitous in the anaerobic wetland sediment (Neill 1995; Chanton et al. 1997); however, methane can readily Electronic supplementary material The online version of this article (doi:10.1007/s13157-010-0134-7) contains supplementary material, which is available to authorized users. C. L. Powell : A. Agrawal (*) Environmenal Sciences PhD Program, Wright State University, 3640 Colonel Glenn Highway, Dayton, OH 45435, USA e-mail: abinash.agrawal@wright.edu A. Agrawal Department of Earth & Environmental Sciences, Wright State University, 3640 Colonel Glenn Highway, Dayton, OH 45435, USA Wetlands DOI 10.1007/s13157-010-0134-7