Identification of a novel metabolite in the degradation of pyrene by Mycobacterium sp strain AP1: Actions of the isolate on two- and three-ring polycyclic aromatic hydrocarbons

Mycobacterium sp. strain AP1 grew with pyrene as a sole source of carbon an d energy. The identification of metabolites accumulating during growth sugg ests that this strain initiates its attack on pyrene by either monooxygenat ion or dioxygenation at its C-4, C-5 positions to give trans- or cis-4,5-di hydroxy-4,5-dihydropyrene, respectively. Dehydrogenation of the latter, ort ho cleavage of the resulting diol to form phenanthrene 4,5-dicarboxylic aci d, and subsequent decarboxylation to phenanthrene 4-carboxylic acid lead to degradation of the phenanthrene 4-carboxylic acid via phthalate. A novel m etabolite identified as 6,6'-dihydroxy-2,2'-biphenyl dicarboxylic acid demo nstrates a new branch in the pathway that involves the cleavage of both cen tral rings of pyrene. In addition to pyrene, strain AP1 utilized hexadecane , phenanthrene, and fluoranthene for growth. Pyrene-grown cells oxidized th e methylenic groups of fluorene and acenaphthene and catalyzed the dihydrox ylation and ortho cleavage of one of the rings of naphthalene and phenanthr ene to give 2-carboxycinnamic and diphenic acids, respectively. The catabol ic versatility of strain AP1 and its use of ortho cleavage mechanisms durin g the degradation of polycyclic aromatic hydrocarbons (PAHs) give new insig ht into the role that pyrene-degrading bacterial strains may play in the en vironmental fate of PAH mixtures.