NOVEL ORGANIZATION OF CATECHOL META-PATHWAY GENES IN SPHINGOMONAS SP.HV3 PSKY4 PLASMID

Sphingomonas sp, strain HV3 (formerly Pseudomonas sp. HV3), which degr ades aromatics and chloroaromatics, harbors a mega-plasmid, pSKY4. A s equenced 4 kb fragment of the plasmid reveals a novel gene organizatio n for catechol meta-pathway genes. The putative meta operon starts wit h the cmpF gene encoding a 2-hydroxymuconic semialdehyde hydrolase. Th e gene has a 6 bp overlap with the previously characterized ring-cleav age gene, catechol 2,3-dioxygenase, cmpE. Downstream of cmpE is a 429 bp open reading frame of unknown function, Gene clop C, encoding a 2-h ydroxymuconic semialdehyde dehydrogenase, starts 44 bp further downstr eam. It has the highest homology to 2-hydroxymuconic semialdehyde dehy drogenases of dmp and xyl pathways and to XylC from the marine oligotr oph Cycloclasticus oligotrophus. The gene organization is different fr om other known meta pathways. This is the first report of organization of plasmid-encoded meta-pathway genes in the genus Sphingomonas.