A catabolic pathway for the degradation of chrysene by Pseudoxanthomonas sp PNK-04

Abstract

The chrysene-degrading bacterium Pseudoxanthomonas sp. PNK-04 was isolated from a coal sample. Three novel metabolites, hydroxyphenanthroic acid, 1-hydroxy- 2-naphthoic acid and salicylic acid, were identified by TLC, HPLC and MS. Key enzyme activities, namely 1-hydroxy-2-naphthoate hydroxylase, 1,2-dihydroxynaphthalene dioxygenase, salicylaldehyde dehydrogenase and catechol1,2- dioxygenase, were noted in the cell-free extract. These results suggest that chrysene is catabolized via hydroxyphenanthroic acid, 1-hydroxy-2-naphthoic acid, salicylic acid and catechol. The terminal aromatic metabolite, catechol, is then catabolized by catechol-1,2-dioxygenase to cis, cis-muconic acid, ultimately forming TCA cycle intermediates. Based on these studies, the proposed catabolic pathway for chrysene degradation by strain PNK-04 is chrysene -> hydroxyphenanthroic acid -> 1-hydroxy-2-naphthoic acid -> 1,2-dihydroxynaphthalene -> salicylic acid -> catechol -> cis, cis-muconic acid.