title: Natural attenuation potential of tricholoroethene in wetland plant roots: role of native ammonium-oxidizing microorganisms.
abstract: Bench-scale microcosms with wetland plant roots were investigated to characterize the microbial contributions to contaminant degradation of trichloroethene (TCE) with ammonium. The batch system microcosms consisted of a known mass of wetland plant roots in aerobic growth media where the roots provided both an inoculum of root-associated ammonium-oxidizing microorganisms and a microbial habitat. Aqueous growth media, ammonium, and TCE were replaced weekly in batch microcosms while retaining roots and root-associated biomass. Molecular biology results indicated that ammonium-oxidizing bacteria (AOB) were enriched from wetland plant roots while analysis of contaminant and oxygen concentrations showed that those microorganisms can degrade TCE by aerobic cometabolism. Cometabolism of TCE, at 29 and 46 μg L(-1), was sustainable over the course of 9 weeks, with 20-30 mg L(-1) ammonium-N. However, at 69 μg L(-1) of TCE, ammonium oxidation and TCE cometabolism were completely deactivated in two weeks. This indicated that between 46 and 69 μg L(-1) TCE with 30 mg L(-1) ammonium-N there is a threshold [TCE] below which sustainable cometabolism can be maintained with ammonium as the primary substrate. However, cometabolism-induced microbial deactivation of ammonium oxidation and TCE degradation at 69 μg L(-1) TCE did not result in a lower abundance of the amoA gene in the microcosms, suggesting that the capacity to recover from TCE inhibition was still intact, given time and removal of stress. Our study indicates that microorganisms associated with wetland plant roots can assist in the natural attenuation of TCE in contaminated aquatic environments, such as urban or treatment wetlands, and wetlands impacted by industrial solvents.
authors.affiliation: Department of Earth & Environmental Sciences, Wright State University, 3640 Colonel Glenn Highway, Dayton, OH 45435, USA.
authors.forename: Ke
authors.initials: K
authors.lastname: Qin
authors.affiliation: Department of Systems and Engineering Management, Air Force Institute of Technology, Wright-Patterson Air Force Base, 2950 Hobson Way, WPAFB, OH 45433, USA.
authors.forename: Garrett C
authors.initials: GC
authors.lastname: Struckhoff
authors.affiliation: Department of Earth & Environmental Sciences, Wright State University, 3640 Colonel Glenn Highway, Dayton, OH 45435, USA. Electronic address: abinash.agrawal@wright.edu.
authors.forename: Abinash
authors.initials: A
authors.lastname: Agrawal
authors.affiliation: Department of Systems and Engineering Management, Air Force Institute of Technology, Wright-Patterson Air Force Base, 2950 Hobson Way, WPAFB, OH 45433, USA.
authors.forename: Michael L
authors.initials: ML
authors.lastname: Shelley
authors.affiliation: Department of Geology and Environmental Earth Science, Miami University, OH 45056, USA.
authors.forename: Hailiang
authors.initials: H
authors.lastname: Dong
mesh_terms: D064751:Ammonium Compounds / Q000378:metabolism*; D001419:Bacteria / Q000235:genetics / Q000378:metabolism*; D031255:Carex Plant / Q000378:metabolism*; D004269:DNA, Bacterial / Q000032:analysis; D017753:Ecosystem; D010084:Oxidation-Reduction; D018517:Plant Roots / Q000378:metabolism*; D012997:Solvents / Q000378:metabolism; D014241:Trichloroethylene / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000378:metabolism*; D053833:Wetlands
chemical_list: D064751:Ammonium Compounds; D004269:DNA, Bacterial; D012997:Solvents; D014874:Water Pollutants, Chemical; D014241:Trichloroethylene
keywords: Ammonium oxidizers; Biodegradation; Carex comosa; Cometabolism; Treatment wetlands; Trichloroethene