Construction and characterization of two recombinant bacteria that grow onortho- and para-substituted chlorobiphenyls

Cloning and expression of the aromatic ring dehalogenation genes in bipheny l-growing, polychlorinated biphenyl (PCB)-cometabolizing Comamonas testoste roni VP44 resulted in recombinant pathways allowing growth on ortho- and pa ra-chlorobiphenyls (CBs) as a sole carbon source. The recombinant variants were constructed by transformation of strain VP44 with plasmids carrying sp ecific genes for dehalogenation of chlorobenzoates (CBAs). Plasmid pE43 car ries the Pseudomonas aeruginosa 142 ohb genes coding for the terminal oxyge nase (ISPOHB) of the ortho-halobenzoate 1,2-dioxygenase, whereas plasmid pP C3 contains the Arthrobacter globiformis KZT1 feb genes, which catalyze the hydrolytic para-dechlorination of 4-CBA. The parental strain, VP44, grew o nly on low concentrations of 2- and 4-CB by using the products from the fis sion of the nonchlorinated ring of the CRs (;pentadiene) and accumulated st oichiometric amounts of the corresponding CBAs. The recombinant strains VP4 4(pPC3) and VP44(pE43) grew on, and completely dechlorinated high concentra tions (up to 10 mM), of 4-CBA and 4-CB and 2-CSA and 2-CB, respectively. Ce ll protein yield corresponded to complete oxidation of both biphenyl rings, thus confirming mineralization of the CBs. Hence, the use of CBA dehalogen ase genes appears to be an effective strategy for construction of organisms that will grow on at least some congeners important for remediation of PCB s.