Growth Inhibition by Metabolites of γ-Hexachlorocyclohexane in Sphingobium japonicum UT26

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The growth of a γ-hexachlorocyclohexane (γ-HCH)-degrading bacterium Sphingobium japonicum (formerly Sphingomonas paucimobilis) UT26 in rich medium was inhibited by γ-HCH. This growth inhibition was not observed in a mutant that lacked the initial or second step enzymatic activity for γ-HCH degradation, suggesting that metabolites of γ-HCH are toxic to UT26. Two metabolites of γ-HCH, 2,5-dichlorophenol (2,5-DCP) and 2,5-dichlorohydroquinone (2,5-DCHQ), showed a direct toxic effect on UT26 and other sphingomonad strains. Because only 2,5-DCP accumulated during γ-HCH degradation, 2,5-DCP is thought to be a main compound for growth inhibition.