Transposon-mediated mobilization of chromosomally located catabolic operons of the CAM plasmid by TOL plasmid transposon Tn4652 and CAM plasmid transposon Tn3614

The CAM (camphor degradation) plasmid is integrated into the chromosome of Pseudomonas putida PaW-line strains and is not selftransferable as a plasmid via conjugation. Our results show that the mobilization of chromosomally located CAM and the integration of cam-operons into the chromosome of the new Cam+ transconjugants is a recA-independent process mediated by transposons Tn4652 (17 kbp) and Tn3614 (7·2 kbp). Transposon Tn3614 is apparently identical to the left-hand and the right-hand sequences of the TOL plasmid pWWO transposon Tn4654. The insertion of Tn401 inside the left-hand terminal IR of Tn4652 completely inhibited the mobilization of CAM. According to our data transposons Tn4652 and Tn3614 together with CAM plasmid catabolic operons are integrated into the chromosome. We propose that in eseudomonads the transposons Tn4652 and Tn3614 play a key role in the evolution and spread of new catabolic plasmids in nature.