title: The corrinoid cofactor of reductive dehalogenases affects dechlorination rates and extents in organohalide-respiring Dehalococcoides mccartyi.
abstract: Corrinoid auxotrophic organohalide-respiring Dehalococcoides mccartyi (Dhc) strains are keystone bacteria for reductive dechlorination of toxic and carcinogenic chloroorganic contaminants. We demonstrate that the lower base attached to the essential corrinoid cofactor of reductive dehalogenase (RDase) enzyme systems modulates dechlorination activity and affects the vinyl chloride (VC) RDases BvcA and VcrA differently. Amendment of 5,6-dimethylbenzimidazolyl-cobamide (DMB-Cba) to Dhc strain BAV1 and strain GT cultures supported cis-1,2-dichloroethene-to-ethene reductive dechlorination at rates of 107.0 (±12.0) μM and 67.4 (±1.4) μM Cl(-) released per day, respectively. Strain BAV1, expressing the BvcA RDase, reductively dechlorinated VC to ethene, although at up to fivefold lower rates in cultures amended with cobamides carrying 5-methylbenzimidazole (5-MeBza), 5-methoxybenzimidazole (5-OMeBza) or benzimidazole (Bza) as the lower base. In contrast, strain GT harboring the VcrA RDase failed to grow and dechlorinate VC to ethene in medium amended with 5-OMeBza-Cba or Bza-Cba. The amendment with DMB to inactive strain GT cultures restored the VC-to-ethene-dechlorinating phenotype and intracellular DMB-Cba was produced, demonstrating cobamide uptake and remodeling. The distinct responses of Dhc strains with BvcA versus VcrA RDases to different cobamides implicate that the lower base exerts control over Dhc reductive dechlorination rates and extents (that is, detoxification), and therefore the dynamics of Dhc strains with discrete reductive dechlorination capabilities. These findings emphasize that the role of the corrinoid/lower base synthesizing community must be understood to predict strain-specific Dhc activity and achieve efficacious contaminated site cleanup.
authors.affiliation: Department of Microbiology, University of Tennessee, Knoxville, TN, USA.|Center for Environmental Biotechnology, University of Tennessee, Knoxville, TN, USA.|Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA.|Joint Institute for Biological Sciences (JIBS), Oak Ridge National Laboratory, Oak Ridge, TN, USA.
authors.forename: Jun
authors.initials: J
authors.lastname: Yan
authors.affiliation: Department of Microbiology, University of Tennessee, Knoxville, TN, USA.|Center for Environmental Biotechnology, University of Tennessee, Knoxville, TN, USA.|Department of Civil and Environmental Engineering, University of Tennessee, Knoxville, TN, USA.
authors.forename: Burcu
authors.initials: B
authors.lastname: Şimşir
authors.affiliation: Department of Chemistry, University of Tennessee, Knoxville, TN, USA.
authors.forename: Abigail T
authors.initials: AT
authors.lastname: Farmer
authors.affiliation: Department of Microbiology, University of Tennessee, Knoxville, TN, USA.|Center for Environmental Biotechnology, University of Tennessee, Knoxville, TN, USA.|Department of Civil and Environmental Engineering, University of Tennessee, Knoxville, TN, USA.
authors.forename: Meng
authors.initials: M
authors.lastname: Bi
authors.affiliation: Department of Microbiology, University of Tennessee, Knoxville, TN, USA.|Center for Environmental Biotechnology, University of Tennessee, Knoxville, TN, USA.|Department of Civil and Environmental Engineering, University of Tennessee, Knoxville, TN, USA.
authors.forename: Yi
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Department of Chemistry, University of Tennessee, Knoxville, TN, USA.
authors.forename: Shawn R
authors.initials: SR
authors.lastname: Campagna
authors.affiliation: Department of Microbiology, University of Tennessee, Knoxville, TN, USA.|Center for Environmental Biotechnology, University of Tennessee, Knoxville, TN, USA.|Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA.|Joint Institute for Biological Sciences (JIBS), Oak Ridge National Laboratory, Oak Ridge, TN, USA.|Department of Civil and Environmental Engineering, University of Tennessee, Knoxville, TN, USA.
authors.forename: Frank E
authors.initials: FE
authors.lastname: Löffler
mesh_terms: D001562:Benzimidazoles / Q000378:metabolism; D001673:Biodegradation, Environmental; D041862:Chloroflexi / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D003038:Cobamides / Q000378:metabolism*; D004000:Dichloroethylenes / Q000378:metabolism; D005030:Ethylenes / Q000378:metabolism; D054879:Halogenation; D014752:Vinyl Chloride / Q000378:metabolism; D014874:Water Pollutants, Chemical / Q000378:metabolism*
chemical_list: D001562:Benzimidazoles; D003038:Cobamides; D004000:Dichloroethylenes; D005030:Ethylenes; D014874:Water Pollutants, Chemical; C036216:ethylene; C551257:5-methylbenzimidazole; D014752:Vinyl Chloride; C035384:1,2-dichloroethylene