Genomics of Catabolic Plasmids

Catabolic plasmids were discovered in the early 1970s by Chakrabarty, working in the laboratory of Gunsalus. These first plasmids were named SAL, OCT and CAM and encoded the catabolism ofsalicylate14, octane and other short chain linear alkanes15, and camphor73 respectively and were all found in strains of Pseudomonas. Shortly after, a naphthalene catabolic plasmid NAH was reported by Dunn from the same laboratory22 and then the TOL plasmid, now known as pWW0,was independently discovered and reported by Nakazawa and Yokota56 Williams and Murray97, and Wong and Dunn101, both also in Pseudomonas host strains. Given the remarkable taxonomic schisms that have more recently taken place within the genus of Pseudomonas since the advent of 16S rRNA gene sequences, all the host strains for these primary catabolic plasmids have remained solidly within the now much more narrowly defined genus of Pseudomonas. But however much the initial breakthrough owes to Pseudomonas, it is now clear three decades later that catabolic plasmids are comprehensively distributed across a very broad range of saprophytic soil bacteria.