The ability of Pseudomonas sp. 8909N to grow using Naphthalene and salicylate as the sole source of carbon and energy is mediated by the presence of an 80-kb conjugative pBS1145 plasmid in this strain. Structural genes for naphthalene degradation in pBS1145 plasmid are homologous to those in the known NAH7 plasmid. Conjugational transfer of pBS1145 from the original strain is accompanied by a deletion of a plasmid DNA fragment that does not affect the Nah+Sal+ phenotype. Plasmid pBS1145 specifies a low constitutive level of catechol-2,3-dioxygenase, the key enzyme of the metha-pathway of catechol degradation. Activity of this enzyme is induced in the presence of salicylate. Enzymes of both the metha and ortho-pathway of catechol degradation (catechol-2-3-dioxygenase) were shown to operate in the process of naphthalene degradation in Pseudomonas sp. 8909N. The ability of this strain to bring about transformation of polycyclic aromatic hydrocarbon phenanthrene is also controlled by pBS1145 plasmid.