Metabolism of fluoranthene by Mycobacterium sp. strain AP1.

The pyrene-degrading Mycobacterium strain AP1 was found to utilize fluoranthene as a sole source of carbon and energy. Identification of metabolites formed from fluoranthene (by growing cells and washed-cell suspensions), the kinetics of metabolite accumulation, and metabolite-feeding studies all indicated that strain AP1 oxidizes fluoranthene using three alternative routes. The first route is initiated by dioxygenation at C-7 and C-8 and, following meta cleavage and pyruvate release, produces a hydroxyacenaphthoic acid that is decarboxylated to acenaphthenone (V). Monooxygenation of this ketone to the quinone and subsequent hydrolysis generates naphthalene-1,8-dicarboxylic acid (IV), which is further degraded via benzene-1,2,3-tricarboxylic acid (III). A second route involves dioxygenation at C-1 and C-2, followed by dehydrogenation and meta cleavage of the resulting diol. A two-carbon fragment excision of the meta cleavage product yields 9-fluorenone-1-carboxylic acid (II), which appears to undergo angular dioxygenation and further degradation to produce benzene-1,2,3-tricarboxylic acid (III), merging this route with the 7,8-dioxygenation route. Decarboxylation of benzene-1,2,3-tricarboxylic acid to phthalate (VIII), as well as further oxidation of the latter, would connect both routes with the central metabolism. The identification of Z-9-carboxymethylenefluorene-1-carboxylic acid (I) suggests a third route for fluoranthene degradation involving dioxygenation at C-2, C-3, and ortho cleavage. There is no evidence of any further degradation of this compound.