Reductive dechlorination of β-hexachlorocyclohexane (β-HCH) by a Dehalobacter species in coculture with a Sedimentibacter sp.

An anaerobic coculture was enriched from a hexachlorocyclohexane (HCH) polluted soil. The coculture reductively dechlorinates the β-HCH isomer to benzene and chlorobenzene in a ratio of 0.5-2 depending on the amount of β-HCH degraded. The culture grows with H2 as electron donor and β-HCH as electron acceptor, indicating that dechlorination is a respiratory process. Phylogenetic analysis indicated that the coculture consists of two bacteria that are both related to gram-positive bacteria with a low G + C content of the DNA. One bacterium was identified as a Dehalobacter sp. This bacterium is responsible for the dechlorination. The other bacterium was isolated and characterized as being a Sedimentibacter sp. This strain is not able to dechlorinate β-HCH. The Dehalobacter sp. requires the presence of Sedimentibacter for growth and dechlorination, but the function of the latter bacterium is not clear. This is the first report on the metabolic dechlorination of β-HCH by a defined anaerobic bacterial culture.