A 90-kilobase conjugative chromosomal element coding for biphenyl and salicylate catabolism in Pseudomonas putida KF715

The biphenyl and salicylate metabolic pathways in Pseudomonas putida KP715 are chromosomally encoded. The bph gene cluster coding for the conversion o f biphenyl to benzoic acid and the sal gene cluster coding for the salicyla te meta-pathway were obtained, from the KF715 genomic cosmid libraries. The se two gene clusters were separated by 10-kb DNA and were highly prone to d eletion when KF715 was grown in nutrient medium. Two types of deletions too k place at the region including only the bph genes (ca. 40 kb) or at the re gion including both the bph and sal genes (ca. 70 kb). A 90-kb, DNA region, including both the bph and sal genes (termed the bph-sal element), was tra nsferred by conjugation from KP715 to P. putida AC30. Such transconjugants gained the ability to grow on biphenyl and salicylate as the sole sources o f carbon. The bph and sal element was located on the chromosome of the reci pient. The bph.-sal element in strain AC30 was also highly prone to deletio n; however, it could be mobilized to the chromosome of P. putida KT2440 and the two deletion mutants of KF715.