Search

Commercial formulations of hexachlorocyclohexane (HCH) consist of a mixture of four isomers, α, β, γ and δ. All these four isomers are toxic and recalcitrant pollutants. Sphingobium (formerly Sphingomonas) sp. strain BHC-A is able to degrade all four HCH isomers. Eight lin genes responsible for the degradation of γ-HCH in BHC-A were cloned and analysed for their role in the degradation of δ-HCH, and the initial conversion steps in δ-HCH catabolism by LinA and LinB in BHC-A were found. LinA dehydrochlorinated δ-HCH to produce 1,3,4,6-tetrachloro-1,4-cyclohexadiene (1,4-TCDN) via δ-pentachlorocyclohexene (δ-PCCH). Subsequently, both 1,4-TCDN and δ-PCCH are catalysed by LinB via two successive rounds of hydrolytic dechlorinations to form 2,5-dichloro-2,5-cyclohexadiene-1,4-diol (2,5-DDOL) and 2,3,5-trichloro-5-cyclohexene-1,4-diol (2,3,5-TCDL) respectively. LinB could also catalyse the hydrolytic dechlorination of δ-HCH to 2,3,5,6-tetrachloro-1,4-cyclohexanediol (TDOL) via 2,3,4,5,6-pentachlorocyclohexanol (PCHL). [ABSTRACT FROM AUTHOR]