The role of dehalorespiring bacteria in the reductive dechlorination of polychlorinated biphenyls in Baltimore harbor sediment microcosms

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dc.contributor.advisorSowers, Kevin Ren_US
dc.contributor.authorFagervold, Sonja Kristineen_US
dc.contributor.departmentMarine-Estuarine-Environmental Sciencesen_US
dc.contributor.publisherDigital Repository at the University of Marylanden_US
dc.contributor.publisherUniversity of Maryland (College Park, Md.)en_US
dc.date.accessioned2007-06-22T05:32:23Z
dc.date.available2007-06-22T05:32:23Z
dc.date.issued2007-03-29
dc.description.abstractBaltimore Harbor sediment microcosms were incubated with the 12 most predominant congeners in Aroclor 1260 and their intermediate products to identify the major dechlorination pathways. Most congeners were dechlorinated in the meta position, although some dechlorination in the para and ortho positions was observed. The major dechlorination products were tetrachlorinated biphenyls with unflanked chlorines. Specific dechlorination rates of parent and intermediate PCB congeners were determined to identify the rate limiting reactions. To identify the microorganisms responsible for the dechlorination pathways, I developed PCR primers specific for the 16S rRNA genes of known PCB dehalogenating bacteria. These PCR primers were used in conjunction with DGGE to selectively identify the microorganisms that catalyzed each dechlorination reaction. Only three phylotypes were identified that catalyze the dechlorination of Aroclor 1260, and the selective activities of these phylotypes were determined. Phylotype DEH10 had high sequence similarity to Dehalococcoides spp., while phylotype SF1 had high sequence similarity to the o-17/DF-1 group of PCB dechlorinating bacteria. The third phylotype had 100% sequence similarity to the ortho-dechlorinating bacterium o-17 described previously from Baltimore Harbor sediments. Most dechlorination reactions for all three phylotypes were growth-linked, indicating that PCB-impacted environments have the potential to sustain populations of PCB dechlorinating organisms. To investigate whether bioaugmentation would be feasible for bioremediation of PCB contaminated sites, Baltimore Harbor sediment microcosms were supplemented with known dechlorinators and their effects on PCBs dechlorination patterns determined. The addition of different dechlorinators resulted in different dechlorination patterns. Finally, novel putative reductive dehalogenases were identified from the PCB dechlorinating bacterium DF-1 using degenerate PCR primers. Comparative sequence analyses indicated that they had high sequence similarity to both confirmed and putative dehalogenases from several Dehalococcoides species. In conclusion, microorganisms that can dechlorinate Aroclor 1260 have been identified for the first time and dechlorination of congener mixtures was shown to occur by the growth-linked complementary activities of bacterial consortia within the Chloroflexi. Demonstration that bioaugmentation with these organisms can influence rates and pathways of dechlorination, combined with the development of molecular assay for monitoring their fate, provide potentially valuable tools for the development of bioremedial strategies for PCB contaminated sediments.en_US
dc.format.extent9157451 bytes
dc.format.mimetypeapplication/pdf
dc.identifier.urihttp://hdl.handle.net/1903/6723
dc.language.isoen_US
dc.subject.pqcontrolledEnvironmental Sciencesen_US
dc.subject.pqcontrolledBiology, Molecularen_US
dc.subject.pqcontrolledBiology, Microbiologyen_US
dc.subject.pquncontrolledPCBen_US
dc.subject.pquncontrolledreductive dechlorinationen_US
dc.subject.pquncontrolledAroclor 1260en_US
dc.subject.pquncontrolled16S rRNAen_US
dc.subject.pquncontrolledanaerobicen_US
dc.subject.pquncontrolledChloroflexien_US
dc.titleThe role of dehalorespiring bacteria in the reductive dechlorination of polychlorinated biphenyls in Baltimore harbor sediment microcosmsen_US
dc.typeDissertationen_US

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