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摘要
Aim: To isolate gamma-hexachlorocyclohexane (HCH)-degrading bacteria from contaminated soil and characterize the metabolites formed and the genes involved in the degradation pathway.
Methods and Results: A bacterial strain Xanthomonas sp. ICH12, capable of biodegrading gamma-HCH was isolated from HCH-contaminated soil. DNA-colony hybridization method was employed to detect bacterial populations containing specific gene sequences of the gamma-HCH degradation pathway. HnA (dehydrodehalogenase), linB (hydrolytic dehalogenase) and UnC (dehydrogenase) from a Sphingomonas paucimobilis UT26, reportedly possessing gamma-HCH degradation activity, were used as gene probes against isolated colonies. The isolate was found to grow and utilize gamma-HCH as the sole carbon and energy source. The 16S ribosomal RNA gene sequence of the isolate resulted in its identification as a Xanthomonas species, and we designated it as strain ICH12. During the degradation of gamma-HCH by ICH12, formation of two intermediates, gamma-2,3,4,5,6-pentachlorocyclohexene (gamma-PCCH), and 2,5-dichlorobenzoquinone (2,5-DCBQ), were identified by gas chromatography-mass spectrometric (GCMS) analysis. While gamma-PCCH was reported previously, 2,5-dichlorohydroquinone was a novel metabolite from HCH degradation.
Conclusions: A Xanthomonas sp. for gamma-HCH degradation from a contaminated soil was isolated. y-HCH was utilized as sole source of carbon and energy, and the degradation proceeds by successive dechlorination. Two degradation products gamma-PCCH and 2,5-DCBQ were characterized, and the latter metabolite was not known in contrasts with the previous studies. The present work, for the first time, demonstrates the potential of a Xanthomonas species to degrade a recalcitrant and widespread pollutant like y-HCH.
Significance and Impact of the Study: This study demonstrates the isolation and characterization of a novel HCH-clegrading bacterium. Further results provide an insight into the novel degradation pathway which may exist in diverse HCH-degrading bacteria in contaminated soils leading to bioremediation of y-HCH.
- 出版日期2007-6
