Mycobacterium aromativorans JS19b1T degrades phenanthrene through C-1,2, C-3,4 and C-9,10 dioxygenation pathways

Mycobacterium aromativorans strain JS19b1T can utilize phenanthrene as a sole source of carbon and energy. Strain JS19b1T degrades phenanthrene through highly branched metabolic pathways, including dioxygenation on C-1,2, C-3,4 and C-9,10 positions and ring opening by both ortho- and meta-cleavage. The presence of novel metabolic pathways was confirmed by replacement cultivation using synthetic metabolite standards. The metabolites were isolated and identified by gas chromatography-mass spectrometry. Both ortho and meta-cleavage products of 1,2- and 3,4-dihydroxyphenanthrene were detected. Two ortho-cleavage products, 1-[(E)-2-carboxyvinyl]-2-naphthoic acid and 2-[(E)-2-carboxyvinyl]-1-napthoic acid were further metabolized to naphthalene-1,2-dicarboxylic acid and then to 1,2-dihydroxynaphthalene, which can also be produced from the meta-cleavage products hydroxynaphthoic acids. These results suggest that part of the branched pathways is merged into 1,2-dihydroxynaphthalene. The concentrations of the products from C-9,10 dioxygenation were higher than those from other pathways. C-9,10 dioxygenation of phenanthrene produced phthalic acid through decarboxylation and mono-/di-oxygenation. The diverse phenanthrene metabolic pathways in JS19b1T give a new insight of the bacterial degradation of polycyclic aromatic hydrocarbons.

► Mycobacterium aromativorans JS19b1T utilizes PAHs for growth. ► JS19b1T degrades phenanthrene via multi-site dioxygenation and ortho-/meta-cleavage. ► Part of the branched pathways is merged into 1,2-dihydroxynaphthalene. ► Products from C-9,10 dioxygenation dominate. ► The 9,10-dioxygenation pathway is merged to form phthalate.