Induction of bphA, encoding biphenyl dioxygenase, in two polychlorinated biphenyl-degrading bacteria, psychrotolerant Pseudomonas strain Cam-1 and mesophilic Burkholderia strain LB400.
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-Gm(r) 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 degrees 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 degrees 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 degrees C was approximately five times less than the level in LB400-1 grown at 30 degrees C. Thus, there are substantial differences in the effects of physical and chemical environmental conditions on genetic regulation of PCB degradation in different bacteria.
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Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.
Mohn
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D001673:Biodegradation, Environmental; D019117:Burkholderia / Q000378:metabolism*; D003080:Cold Temperature; D004790:Enzyme Induction; D015964:Gene Expression Regulation, Bacterial; D017930:Genes, Reporter; D005822:Genetic Vectors; D006358:Hot Temperature; D007506:Iron-Sulfur Proteins; D007763:Lac Operon; D008969:Molecular Sequence Data; D010105:Oxygenases / Q000235:genetics*; D011078:Polychlorinated Biphenyls / Q000378:metabolism*; D011549:Pseudomonas / Q000378:metabolism*; D012641:Selection, Genetic
D007506:Iron-Sulfur Proteins; D011078:Polychlorinated Biphenyls; D010105:Oxygenases; C074161:biphenyl-2,3-dioxygenase