A novel pathway for the biodegradation of γ-hexachlorocyclohexane by a Xanthomonas sp. strain ICH12
Article first published online: 2 NOV 2006
Journal of Applied Microbiology
Volume 102, Issue 6, pages 1468–1478, June 2007
How to Cite
Manickam, N., Misra, R. and Mayilraj, S. (2007), A novel pathway for the biodegradation of γ-hexachlorocyclohexane by a Xanthomonas sp. strain ICH12. Journal of Applied Microbiology, 102: 1468–1478. doi: 10.1111/j.1365-2672.2006.03209.x
- Issue published online: 2 NOV 2006
- Article first published online: 2 NOV 2006
- 2006/0797: Received 2 June 2006, revised 19 August 2006 and accepted 13 November 2006
Aim: To isolate γ-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 γ- HCH was isolated from HCH-contaminated soil. DNA-colony hybridization method was employed to detect bacterial populations containing specific gene sequences of the γ-HCH degradation pathway. linA (dehydrodehalogenase), linB (hydrolytic dehalogenase) and linC (dehydrogenase) from a Sphingomonas paucimobilis UT26, reportedly possessing γ-HCH degradation activity, were used as gene probes against isolated colonies. The isolate was found to grow and utilize γ-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 γ-HCH by ICH12, formation of two intermediates, γ-2,3,4,5,6-pentachlorocyclohexene (γ-PCCH), and 2,5-dichlorobenzoquinone (2,5-DCBQ), were identified by gas chromatography-mass spectrometric (GC-MS) analysis. While γ-PCCH was reported previously, 2,5-dichlorohydroquinone was a novel metabolite from HCH degradation.
Conclusions: A Xanthomonas sp. for γ-HCH degradation from a contaminated soil was isolated. γ-HCH was utilized as sole source of carbon and energy, and the degradation proceeds by successive dechlorination. Two degradation products γ-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 γ-HCH.
Significance and Impact of the Study: This study demonstrates the isolation and characterization of a novel HCH-degrading 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 γ-HCH.