INCREASED EXPRESSION OF THE PLASMID-DETERMINED 2,3-DIHYDROXYBIPHENYL DIOXYGENASE GENE IN STRAINS OF ESCHERICHIA-COLI, PSEUDOMONAS-PUTIDA AND PSEUDOMONAS-AERUGINOSA

A 6.5-kb EcoRI fragment containing the gene encoding 2,3-dihydroxybiphenyl dioxygenase from the plasmid pBS312 was cloned into broad host range plasmid RSF1010 and expressed in Escherichia coli, Pseudomonas putida and Pseudomonas aeruginosa strains. The increased expression of the gene was orientation-dependent and probably due to the transcription read through from the streptomycin promoter of the vector. Subcloning experiments of the PstI fragments of pBS312 plasmid using vector pBR322 revealed that the bphC gene encoding 2,3-dihydroxybiphenyl dioxygenase is localized on the 2.1-kb fragment. In Escherichia coli JM109, transformed by the plasmid pBS314 carrying the 2.1-kb insert in orientation which allowed expression of the bphC gene from the ampicillin promoter of pBR322, the enzyme activity of 2,3-dihydroxybiphenyl dioxygenase was ten times higher than that in parental strain Pseudomonas putida SU83. The results presented show the first case of the increased expression of Pseudomonas degradative gene in Escherichia coli.