DEGRADATION OF PYRENE, BENZ[A]ANTHRACENE, AND BENZO[A]PYRENE BY MYCOBACTERIUM SP STRAIN RJGII-135, ISOLATED FROM A FORMER COAL-GASIFICATIONSITE

The degradation of three polycyclic aromatic hydrocarbons (PAH), pyren e (PYR), benz[a]anthracene (BAA), and benzo[a]pyrene (BaP), by Mycobac terium sp. strain RJGII-135 was studied. The bacterium was isolated fr om an abandoned coal gasification site soil by analog enrichment techn iques and found to mineralize [C-14]PYR. Further degradation studies w ith PYR showed three metabolites formed by Mycobacterium sp. strain RJ GII-135, including 4,5-phenanthrene-dicarboxylic acid not previously i solated, 4-phenanthrene-carboxylic acid, and 4,5-pyrene-dihydrodiol. A t least two dihydrodiols, 5,6-BAA-dihydrodiol and 10,11-BAA-dihydrodio l, were confirmed by high-resolution mass spectral and fluorescence an alyses as products of the biodegradation of BAA by Mycobacterium sp. s train RJGII-135. Additionally, a cleavage product of BAA was also isol ated. Mass spectra and fluorescence data support two different routes for the degradation of BaP by Mycobacterium sp. strain RJGII-135, The 7,8-BaP-dihydrodiol and three cleavage products of BaP, including 4,5- chrysene-dicarboxylic acid and a dihydro-pyrene-carboxylic acid metabo lite, have been isolated and identified as degradation products formed by Mycobacterium sp. strain RJGII-135. These latter results represent the first example of the isolation of BaP ring fission products forme d by a bacterial isolate. We propose that while this bacterium appears to attack only one site of the PYR molecule, it is capable of degradi ng different sites of the BAA and BaP molecules, and although the site s of attack may be different, the ability of this bacterium to degrade these PAH is well supported. The proposed pathways for biodegradation of these compounds by this Mycobacterium sp. strain RJGII-135 support the dioxygenase enzymatic processes reported previously for other bac teria. Microorganisms like Mycobacterium sp. strain RJGII-135 will be invaluable in attaining the goal of remediation of sites containing mi xtures of these PAH.