Metabolomics of hexachlorocyclohexane (HCH) transformation: ratio of LinA to LinB determines metabolic fate of HCH isomers

Authors

  • Birgit Geueke,

    1. Department of Environmental Microbiology, Swiss Federal Institute for Aquatic Science and Technology (Eawag), Dübendorf, Switzerland
    Search for more papers by this author
  • Nidhi Garg,

    1. Department of Environmental Microbiology, Swiss Federal Institute for Aquatic Science and Technology (Eawag), Dübendorf, Switzerland
    2. Department of Zoology, University of Delhi, Delhi, India
    Search for more papers by this author
  • Sneha Ghosh,

    1. Department of Environmental Microbiology, Swiss Federal Institute for Aquatic Science and Technology (Eawag), Dübendorf, Switzerland
    2. KIIT University, Bhubaneswar, India
    Search for more papers by this author
  • Thomas Fleischmann,

    1. Department of Environmental Microbiology, Swiss Federal Institute for Aquatic Science and Technology (Eawag), Dübendorf, Switzerland
    Search for more papers by this author
  • Christof Holliger,

    1. Laboratory for Environmental Biotechnology, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
    Search for more papers by this author
  • Rup Lal,

    1. Department of Zoology, University of Delhi, Delhi, India
    Search for more papers by this author
  • Hans-Peter E. Kohler

    Corresponding author
    • Department of Environmental Microbiology, Swiss Federal Institute for Aquatic Science and Technology (Eawag), Dübendorf, Switzerland
    Search for more papers by this author

For correspondence. E-mail kohler@eawag.ch; Tel. (+41) 58 765 5521; Fax (+41) 58 765 5547.

Summary

Although the production and use of technical hexachlorocyclohexane (HCH) and lindane (the purified insecticidal isomer γ-HCH) are prohibited in most countries, residual concentrations still constitute an immense environmental burden. Many studies describe the mineralization of γ-HCH by bacterial strains under aerobic conditions. However, the metabolic fate of the other HCH isomers is not well known. In this study, we investigated the transformation of α-, β-, γ-, δ-, ε-HCH, and a heptachlorocyclohexane isomer in the presence of varying ratios of the two enzymes that initiate γ-HCH degradation, a dehydrochlorinase (LinA) and a haloalkane dehalogenase (LinB). Each substrate yielded a unique metabolic profile that was strongly dependent on the enzyme ratio. Comparison of these results to those of in vivo experiments with different bacterial isolates showed that HCH transformation in the tested strains was highly optimized towards productive metabolism of γ-HCH and that under these conditions other HCH-isomers were metabolized to mixtures of dehydrochlorinated and hydroxylated side-products. In view of these results, bioremediation efforts need very careful planning and toxicities of accumulating metabolites need to be evaluated.

Ancillary