Complete nucleotide sequence and evolutionary significance of a chromosomally encoded naphthalene-degradation lower pathway from Pseudomonas stutzeriAN10

Pseudomonas stutzeri strain AN10 is a naphthalene-degrading strain whose di ssimilatory genes are chromosomally encoded. We sequenced the entire naphth alene-degradation lower pathway of P. stutzeri AN10, this being, together w ith the upper-pathway reported previously (Bosch R. et al., 1999a. Gene 236 , 149-157) the first complete DNA sequence for an entire naphthalene-catabo lic pathway. Eleven open reading frames were identified. The mahGTHINLOMKJ; genes encode enzymes for the metabolism of salicylate to pyruvate and acet yl-CoA, and nahR encodes the NahR regulatory protein. Our findings suggest that catabolic modules were recruited through transposition events and reco mbination among mpA-like genes, and subsequent rearrangements and deletions of non-essential DNA fragments allowed the formation of the actual catabol ic pathway. Our results also suggest that the genes encoding the xylene,:to luene-degradation enzymes of P. putida mt-2 (pWW0) have coexisted with the nah genes of the P. stutzeri AN10 ancestral genome. This could allow the se lection, via recombination events among homologous genes, for a combination of genes enabling the metabolism of a given aromatic compound in the ances tral host strain, Such events accelerate the evolution of modern catabolic pathways and provide new genetic material to the environment, ultimately re sulting in improved, natural, bioremediation potential. (C) 2000 Elsevier S cience B.V. All rights reserved.