title: Diversity of dechlorination pathways and organohalide respiring bacteria in chlorobenzene dechlorinating enrichment cultures originating from river sludge.
abstract: Anaerobic reductive dechlorination of hexachlorobenzene (HCB) and three isomers of tetrachlorobenzene (TeCB) (1,2,3,4-, 1,2,3,5- and 1,2,4,5-TeCB) was investigated in microcosms containing chloroaromatic contaminated river sediment. All chlorobenzenes were dechlorinated to dichlorobenzene (DCB) or monochlorobenzene. From the sediment, a methanogenic sediment-free culture was obtained which dechlorinated HCB, pentachlorobenzene, three TeCB isomers, three trichlorobenzene (TCB) isomers (1,2,3-, 1,2,4- and 1,3,5-TCB) and 1,2-DCB. Dechlorination involved multiple pathways including the removal of doubly flanked, singly flanked and isolated chlorine substituents. 454-pyrosequencing of partial bacterial 16S rRNA genes amplified from selected chlorobenzene dechlorinating sediment-free enrichment cultures revealed the presence of a variety of bacterial species, including Dehalobacter and Dehalococcoides mccartyi, that were previously documented as organohalide respiring bacteria. A genus with apparent close relationship to Desulfitobacterium that also has been associated with organohalide respiration, composed the major fraction of the operational taxonomic units (OTUs). Another major OTU was linked with Sedimentibacter sp., a genus that was previously identified in strict co-cultures of consortia reductively dehalogenating chlorinated compounds. Our data point towards the existence of multiple interactions within highly chlorinated benzene dechlorinating communities.
authors.affiliation: Division of Soil and Water Management, KU Leuven, Kasteelpark Arenberg 20, 3001, Leuven, Belgium.
authors.forename: Pieter
authors.initials: P
authors.lastname: Vandermeeren
authors.forename: Steffi
authors.initials: S
authors.lastname: Herrmann
authors.forename: Danuta
authors.initials: D
authors.lastname: Cichocka
authors.forename: Pieter
authors.initials: P
authors.lastname: Busschaert
authors.forename: Bart
authors.initials: B
authors.lastname: Lievens
authors.forename: Hans-Hermann
authors.initials: HH
authors.lastname: Richnow
authors.forename: Dirk
authors.initials: D
authors.lastname: Springael
mesh_terms: D001673:Biodegradation, Environmental; D002722:Chlorobenzenes / Q000378:metabolism*; D041862:Chloroflexi / Q000235:genetics / Q000378:metabolism*; D012336:RNA, Ribosomal, 16S; D045483:Rivers / Q000382:microbiology; D012722:Sewage / Q000382:microbiology*
chemical_list: D002722:Chlorobenzenes; D012336:RNA, Ribosomal, 16S; D012722:Sewage; C036720:trichlorobenzene; C003060:pentachlorobenzene; C031294:chlorobenzene