title: Abundance and activity of vinyl chloride (VC)-oxidizing bacteria in a dilute groundwater VC plume biostimulated with oxygen and ethene.
abstract: Clean-up of vinyl chloride (VC)-contaminated groundwater could be enhanced by stimulating aerobic VC-oxidizing bacterial populations (e.g., methanotrophs) with amendments such as molecular oxygen. In addition, ethene gas injection could further stimulate a different group of aerobic ethene- and VC-oxidizing bacteria called "etheneotrophs." We estimated the abundance and activity of these different VC-oxidizing bacteria in portions of a dilute groundwater VC plume subjected to oxygen and ethene biostimulation. Pyrosequencing of 16S rRNA genes, amplified from community DNA extracted from five groundwater monitoring wells, revealed that Proteobacteria dominated the microbial community. Among the Proteobacteria, methanotroph relative abundance was 6.00 % (well RB52I), 2.81 % (well RB46D), 56.3 % (well RB58I), 23.8 % (well RB63I), and 2.57 % (well RB64I). Reverse transcription qPCR (RT-qPCR) analysis was used to determined methanotroph and etheneotroph functional gene expression from selected monitoring wells. Resulting transcript per gene ratios for methanotroph functional genes (pmoA and mmoX) were 0.013 (RB46D), 0.017 (RB63I), 0.112 (RB64I), and 0.004 (RB46D), 0.239 (RB63I), and 0.199 (RB64I), respectively. Transcript per gene ratios for etheneotroph functional genes (etnC and etnE) were 0.37 (RB46D), 0.81 (RB63I), 5.85 (RB64I), and 0.38 (RB46D), 0.67 (RB63I), and 2.28 (RB64I), respectively. When considered along with geochemical and contaminant data from these wells, our RT-qPCR results suggest that methanotrophs and etheneotrophs were participating in VC cometabolism. We conclude that these molecular diagnostic techniques could be helpful to site managers interested in documenting the effectiveness of VC bioremediation strategies.
authors.affiliation: Department of Civil and Environmental Engineering, The University of Iowa, 4105 Seamans Center, Iowa City, IA, 52242, USA. tmattes@engineering.uiowa.edu.
authors.forename: Timothy E
authors.initials: TE
authors.lastname: Mattes
authors.affiliation: Department of Civil and Environmental Engineering, The University of Iowa, 4105 Seamans Center, Iowa City, IA, 52242, USA.
authors.forename: Yang Oh
authors.initials: YO
authors.lastname: Jin
authors.affiliation: Department of Civil and Environmental Engineering, The University of Iowa, 4105 Seamans Center, Iowa City, IA, 52242, USA.
authors.forename: Joshua
authors.initials: J
authors.lastname: Livermore
authors.affiliation: Department of Civil and Environmental Engineering, The University of Iowa, 4105 Seamans Center, Iowa City, IA, 52242, USA.
authors.forename: Meredith
authors.initials: M
authors.lastname: Pearl
authors.affiliation: Department of Civil and Environmental Engineering, The University of Iowa, 4105 Seamans Center, Iowa City, IA, 52242, USA.
authors.forename: Xikun
authors.initials: X
authors.lastname: Liu
mesh_terms: D000332:Aerobiosis; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D005030:Ethylenes / Q000378:metabolism*; D020869:Gene Expression Profiling; D060587:Groundwater / Q000382:microbiology*; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism*; D020560:Proteobacteria / Q000254:growth & development* / Q000378:metabolism*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D014752:Vinyl Chloride / Q000378:metabolism*; D014873:Water Pollutants / Q000378:metabolism*
chemical_list: D004275:DNA, Ribosomal; D005030:Ethylenes; D012336:RNA, Ribosomal, 16S; D014873:Water Pollutants; C036216:ethylene; D010100:Oxygen; D014752:Vinyl Chloride
keywords: 16S pyrosequencing; Bioremediation; Chloroethenes; Cometabolism; Etheneotroph; Methanotroph; QPCR; Vinyl chloride