Analysis of a 2,4,6-trichlorophenol-dehalogenating enrichment culture and isolation of the dehalogenating member Desulfitobacterium frappieri strain TCP-A

An anaerobic, 2,4,6-trichlorophenol ortho-dehalogenating mixed culture was enriched from sediment of the river Saale (Germany). Two isolated dechlorin ating colonies (MK1 and MK2) consisted of rods of different lengths and thi cknesses, indicating heterogeneity. Following subcultivation with thiosulfa te as alternative electron acceptor and cocultivation with Clostridium cele recrescens(T), the 2,4,6-trichlorophenol-dehalogenating bacterium Desulfito bacterium frappieri strain TCP-A was isolated and characterized regarding i ts taxonomic properties and the spectrum of chlorophenols that it dehalogen ated. Four other bacterial strains were coenriched and identified as organi sms with closest phylogenetic relatedness to the Clostridium type strains C . indolis, C. glycolicum, C. hydroxybenzoicum and C. sporosphaeroides (16S rDNA sequence identities of 99.5, 99.2, 94.4, and 93.5%, respectively). Amp lified ribosomal DNA restriction analysis of the original dehalogenating cu ltures MK1 and MK2 (when not exposed to thiosulfate) confirmed the microbia l heterogeneity and revealed the presence of two additional species related to the type strains of C. celerecrescens and Clostridium propionicum. Only one copy of the 16S rRNA genes of Desulfitobacterium frappieri in each of the clone libraries of MK1 and MK2 (containing 136 and 56 clones, respectiv ely) was found by dot-blot hybridization, suggesting a relatively low numbe r of the dehalogenating bacterium within the enrichment culture.