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Applied and Environmental Microbiology, June 2001, p. 2669-2676, Vol. 67, No. 6
0099-2240/01/$04.00+0   DOI: 10.1128/AEM.67.6.2669-2676.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.

Induction of bphA, Encoding Biphenyl Dioxygenase, in Two Polychlorinated Biphenyl-Degrading Bacteria, Psychrotolerant Pseudomonas Strain Cam-1 and Mesophilic Burkholderia Strain LB400

Emma R. Master and William W. Mohn*

Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada

Received 17 October 2000/Accepted 16 March 2001

We investigated induction of biphenyl dioxygenase in the psychrotolerant polychlorinated biphenyl (PCB) degrader Pseudomonas strain Cam-1 and in the mesophilic PCB degrader Burkholderia strain LB400. Using a counterselectable gene replacement vector, we inserted a lacZ-Gmr fusion cassette between chromosomal genes encoding the large subunit (bphA) and small subunit (bphE) of biphenyl dioxygenase in Cam-1 and LB400, generating Cam-10 and LB400-1, respectively. Potential inducers of bphA were added to cell suspensions of Cam-10 and LB400-1 incubated at 30°C, and then beta-galactosidase activity was measured. Biphenyl induced beta-galactosidase activity in Cam-10 to a level approximately six times greater than the basal level in cells incubated with pyruvate. In contrast, the beta-galactosidase activities in LB400-1 incubated with biphenyl and in LB400-1 incubated with pyruvate were indistinguishable. At a concentration of 1 mM, most of the 40 potential inducers tested were inhibitory to induction by biphenyl of beta-galactosidase activity in Cam-10. The exceptions were naphthalene, salicylate, 2-chlorobiphenyl, and 4-chlorobiphenyl, which induced beta-galactosidase activity in Cam-10, although at levels that were no more than 30% of the levels induced by biphenyl. After incubation for 24 h at 7°C, biphenyl induced beta-galactosidase activity in Cam-10 to a level approximately four times greater than the basal level in cells incubated with pyruvate. The constitutive level of beta-galactosidase activity in LB400-1 grown at 15°C was approximately five times less than the level in LB400-1 grown at 30°C. Thus, there are substantial differences in the effects of physical and chemical environmental conditions on genetic regulation of PCB degradation in different bacteria.

* Corresponding author. Mailing address: Department of Microbiology and Immunology, University of British Columbia, 300-6174 University Blvd., Vancouver, B.C., Canada V6T 1Z3. Phone: (604) 822-4285. Fax: (604) 822-6041. E-mail: wmohn{at}interchange.ubc.ca.

Applied and Environmental Microbiology, June 2001, p. 2669-2676, Vol. 67, No. 6
0099-2240/01/$04.00+0   DOI: 10.1128/AEM.67.6.2669-2676.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.


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