title: Rapid Enrichment of Dehalococcoides-Like Bacteria by Partial Hydrophobic Separation.
abstract: Organohalide-respiring bacteria can be difficult to enrich and isolate, which can limit research on these important organisms. The goal of this research was to develop a method to rapidly (minutes to days) enrich these organisms from a mixed community. The method presented is based on the hypothesis that organohalide-respiring bacteria would be more hydrophobic than other bacteria as they dehalogenate hydrophobic compounds. The method developed tests this hypothesis by separating a portion of putative organohalide-respiring bacteria, those phylogenetically related toDehalococcoides mccartyi, at the interface between a hydrophobic organic solvent and an aqueous medium. This novel partial separation technique was tested with a polychlorinated biphenyl-enriched sediment-free culture, a tetrachloroethene-enriched digester sludge culture, and uncontaminated lake sediment. Significantly higher fractions, up to 20.4 times higher, of putative organohalide-respiring bacteria were enriched at the interface between the medium and either hexadecane or trichloroethene. The selective partial separation of these putative organohalide-respiring bacteria occurred after 20 min, strongly suggesting that the separation was a result of physical-chemical interactions between the cell surface and hydrophobic solvent. Dechlorination activity postseparation was verified by the production ofcis-dichloroethene when amended with tetrachloroethene. A longer incubation time of 6 days prior to separation with trichloroethene increased the total number of putative organohalide-respiring bacteria. This method provides a way to quickly separate some of the putative organohalide-respiring bacteria from other bacteria, thereby improving our ability to study multiple and different bacteria of potential interest and improving knowledge of these bacteria.IMPORTANCEOrganohalide-respiring bacteria, bacteria capable of respiring chlorinated contaminants, can be difficult to enrich, which can limit their predictable use for the bioremediation of contaminated sites. This paper describes a method to quickly separateDehalococcoides-like bacteria, a group of organisms containing organohalide-respiring bacteria, from other bacteria in a mixed community. From this work,Dehalococcoides-like bacteria appear to have a hydrophobic cell surface, facilitating a rapid (20 min) partial separation from a mixed culture at the surface of a hydrophobic liquid. This method was verified in a polychlorinated biphenyl-enriched sediment-free culture, an anaerobic digester sludge, and uncontaminated sediment. The method described can drastically reduce the amount of time required to partially separateDehalococcoides-like bacteria from a complex mixed culture, improving researchers' ability to study these important bacteria.
authors.affiliation: Department of Civil, Environmental, and Geo-Engineering, University of Minnesota, Minneapolis, Minnesota, USA.
authors.forename: Hanna R
authors.initials: HR
authors.lastname: Temme
authors.affiliation: Department of Civil, Environmental, and Geo-Engineering, University of Minnesota, Minneapolis, Minnesota, USA.
authors.forename: Kipp
authors.initials: K
authors.lastname: Sande
authors.affiliation: Department of Civil and Environmental Engineering, University of Hawaii at Manoa, Honolulu, Hawaii, USA.
authors.forename: Tao
authors.initials: T
authors.lastname: Yan
authors.affiliation: Department of Civil, Environmental, and Geo-Engineering, University of Minnesota, Minneapolis, Minnesota, USA novak010@umn.edu.
authors.forename: Paige J
authors.initials: PJ
authors.lastname: Novak
mesh_terms: D001673:Biodegradation, Environmental; D041862:Chloroflexi / Q000254:growth & development / Q000378:metabolism*; D005025:Ethylene Dichlorides / Q000378:metabolism*; D019015:Geologic Sediments / Q000382:microbiology; D054879:Halogenation; D057927:Hydrophobic and Hydrophilic Interactions; D011078:Polychlorinated Biphenyls / Q000378:metabolism*; D012722:Sewage / Q000382:microbiology*; D013750:Tetrachloroethylene / Q000378:metabolism*; D014241:Trichloroethylene / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000378:metabolism*
chemical_list: D005025:Ethylene Dichlorides; D012722:Sewage; D014874:Water Pollutants, Chemical; D014241:Trichloroethylene; D011078:Polychlorinated Biphenyls; D013750:Tetrachloroethylene
keywords: Dehalococcoides; dechlorination; enrichment; organohalide-respiring bacteria; separation