title: Stable isotope fractionation of gamma-hexachlorocyclohexane (lindane) during reductive dechlorination by two strains of sulfate-reducing bacteria.
abstract: Carbon isotope fractionation factors were determined with the dichloro elimination of gamma-hexachlorocyclohexane (gamma-HCH) by the sulfate-reducing bacteria Desulfococcus multivorans DSM 2059 and Desulfovibrio gigas DSM 1382. Both strains are known for cometabolic HCH dechlorination. Degradation experiments with gamma-HCH in concentrations of 22-25 gammaM were carried out using benzoate (for D. multivorans) and lactate (for D. gigas) as electron donors, respectively. Gamma-HCH was dechlorinated by both bacterial strains within four weeks, and the metabolites gamma-3,4,5,6-tetrachlorocyclohexene (gamma-TCCH), chlorobenzene (CB), and benzene were formed. The carbon isotope fractionation of gamma-HCH dechlorination was quantified by the Rayleigh model, using a bulk enrichment factor (epsilon C) of -3.9 +/- 0.6 for D. gigas and -3.4 +/- 0.5 for D. multivorans, which correspond to apparent kinetic isotope effect (AKIEc) values of 1.023 +/- 0.004 or 1.02 +/- 0.003 for stepwise Cl-C bond cleavage. The extent and range of isotope fractionation suggest that gamma-HCH dechlorination can be monitored in anoxic environments by compound-specific isotope analysis (CSIA).
authors.affiliation: Department of Isotope Biogeochemistry, Helmholtz Centre for Environmental Research-UFZ, Permoserstrasse 15, 04318 Leipzig, Germany.
authors.forename: Silviu-Laurentiu
authors.initials: SL
authors.lastname: Badea
authors.forename: Carsten
authors.initials: C
authors.lastname: Vogt
authors.forename: Stefanie
authors.initials: S
authors.lastname: Weber
authors.forename: Andrei-Florin
authors.initials: AF
authors.lastname: Danet
authors.forename: Hans-Hermann
authors.initials: HH
authors.lastname: Richnow
mesh_terms: D000693:Anaerobiosis; D001673:Biodegradation, Environmental; D002247:Carbon Isotopes; D005591:Chemical Fractionation; D045286:Desulfovibrio gigas / Q000378:metabolism; D054879:Halogenation; D001556:Hexachlorocyclohexane / Q000737:chemistry* / Q000302:isolation & purification*; D010084:Oxidation-Reduction; D016999:Sulfur-Reducing Bacteria / Q000378:metabolism*
chemical_list: D002247:Carbon Isotopes; D001556:Hexachlorocyclohexane