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Applied and Environmental Microbiology, September 2006, p. 5720-5727, Vol. 72, No. 9
0099-2240/06/$08.00+0     doi:10.1128/AEM.00192-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Haloalkane Dehalogenase LinB Is Responsible for ß- and -Hexachlorocyclohexane Transformation in Sphingobium indicum B90A

Poonam Sharma,^1, Vishakha Raina,^1,2, Rekha Kumari,¹ Shweta Malhotra,¹ Charu Dogra,¹ Hansi Kumari,¹ Hans-Peter E. Kohler,² Hans-Rudolf Buser,³ Christof Holliger,⁴ and Rup Lal^1*

Department of Zoology, University of Delhi, Delhi 110007, India,¹ Department of Environmental Microbiology, Swiss Federal Institute of Aquatic Research and Technology (Eawag), CH 8600 Dübendorf, Switzerland,² Agaroscope FAW Wädenswil, Swiss Federal Research Station, CH 8820 Wädenswil, Switzerland,³ EPFL, ENAC-ISTE, Laboratory of Environmental Biotechnology, CH 1015 Lausanne, Switzerland⁴

Received 25 January 2006/ Accepted 2 June 2006

Incubation of resting cells of Sphingobium indicum B90A, Sphingobium japonicum UT26, and Sphingobium francense Sp+ showed that they were able to transform ß- and -hexachlorocyclohexane (ß- and -HCH, respectively), the most recalcitrant hexachlorocyclohexane isomers, to pentachlorocyclohexanols, but only resting cells of strain B90A could further transform the pentachlorocyclohexanol intermediates to the corresponding tetrachlorocyclohexanediols. Moreover, experiments with resting cells of Escherichia coli expressing the LinB proteins of strains B90A, UT26, and Sp+ indicated that LinB was responsible for these transformations. Purified LinB proteins from all three strains also effected the formation of the respective pentachlorocyclohexanols. Although the three LinB enzymes differ only marginally with respect to amino acid sequence, they showed interesting differences with respect to substrate specificity. When LinB from strain B90A was incubated with ß- and -HCH, the pentachlorocyclohexanol products were further transformed and eventually disappeared from the incubation mixtures. In contrast, the LinB proteins from strains UT26 and Sp+ could not catalyze transformation of the pentachlorocyclohexanols, and these products accumulated in the incubation mixture. A mutant of strain Sp+ lacking linA and linB did not degrade any of the HCH isomers, including ß-HCH, and complementation of this mutant by linB from strain B90A restored the ability to degrade ß- and -HCH.

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* Corresponding author. Mailing address: Department of Zoology, University of Delhi, Delhi 110007, India. Phone: (91)-11-27666254. Fax: (91)-11-27666254. E-mail: duzdel{at}vsnl.com.

P.S. and V.R. contributed equally to this work.

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Applied and Environmental Microbiology, September 2006, p. 5720-5727, Vol. 72, No. 9
0099-2240/06/$08.00+0     doi:10.1128/AEM.00192-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

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