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Applied and Environmental Microbiology, August 1999, p. 3614-3621, Vol. 65, No. 8
0099-2240/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.

Regiospecificity of Dioxygenation of Di- to Pentachlorobiphenyls and Their Degradation to Chlorobenzoates by the bph-Encoded Catabolic Pathway of Burkholderia sp. Strain LB400

Michael Seeger,1,2,3,dagger Marco Zielinski,1 Kenneth N. Timmis,1 and Bernd Hofer1,*

Division of Microbiology, Gesellschaft für Biotechnologische Forschung, Braunschweig, Germany,1 and Departamento de Bioquímica, Facultad de Medicina, Universidad de Chile, Santiago,2 and Departamento de Química, Universidad Técnica Federico Santa María, Valparaíso,3 Chile

Received 17 February 1999/Accepted 7 June 1999

Burkholderia sp. strain LB400 is one of the most potent aerobic polychlorobiphenyl (PCB)-degrading microorganisms that have been characterized. Its PCB-dioxygenating activity originates predominantly or exclusively from the biphenyl dioxygenase encoded by its bph gene cluster. Analysis of the dioxygenation products of several di- to pentachlorinated biphenyls formed by this enzyme revealed a complex dependence of the regiospecificity and the yield of dioxygenation on the substitution patterns of both the oxidized and the nonoxidized rings. No dioxygenolytic attack involving chlorinated meta or para carbons was observed. Therefore, the ability of the enzyme to hydroxylate chlorinated carbons appears to be limited to the ortho position. However, it is not limited to monochlorinated rings, as evidenced by dioxygenation of the 2,4-disubstituted ring at carbons 2 and 3. This site of attack is strikingly different from that of the 2,5-dichlorinated ring, which has been shown to be dihydroxylated at positions 3 and 4 (J. D. Haddock, J. R. Horton, and D. T. Gibson, J. Bacteriol. 177:20-26, 1995). These results demonstrate that a second substituent of ortho-chlorinated rings crucially influences the site of dioxygenation at this ring and thereby determines whether or not the initial chlorobiphenyl oxidation product is further metabolized through the bph-encoded pathway. The 2,4-dichlorinated ring can alternatively be attacked at carbons 5 and 6. The preferred site crucially depends on the substitution pattern of the other ring. The formation of more than a single dioxygenation product was found predominantly with congeners that contain two chlorinated rings, both of which are similarly prone to dioxygenation or one is substituted only at carbon 3.

* Corresponding author. Mailing address: Department of Microbiology, Gesellschaft für Biotechnologische Forschung, Mascheroder Weg 1, D-38124 Braunschweig, Germany. Phone: (49-531) 6181467. Fax: (49-531) 6181411. E-mail: bho{at}gbf.de.

dagger Present address: Departamento de Química, Universidad Técnica Federico Santa María, Valparaíso, Chile.

Applied and Environmental Microbiology, August 1999, p. 3614-3621, Vol. 65, No. 8
0099-2240/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.


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Copyright © 1999 by the American Society for Microbiology. All rights reserved.