Plasmids with easily excisable xylE cassettes.

Two new vectors containing the xylE gene (encoding catechol-2,3-dioxygenase) of Pseudomonas putida were constructed that serve as the source of the xylE cassette. These vectors are based on the kanamycin-resistance-encoding plasmid, pKAN18. The promoter-less xylE gene is flanked by several restriction enzyme sites that allow for easy excision of this gene in the form of a cassette containing a ribosome-binding site, 7 bp upstream from the start codon. These cassettes lack any transcriptional termination signals downstream from the stop codon.