Degradation of phenanthrene and anthracene by cell suspensions of Mycobacterium sp. strain PYR-1

Abstract

Cultures of Mycobacterium sp. strain PYR-1 were dosed with anthracene or phenanthrene and after 14 days of incubation had degraded 92 and 90% of the added anthracene and phenanthrene, respectively. The metabolites were extracted and identified by UV-visible light absorption, high-pressure liquid chromatography retention times, mass spectrometry, (1)H and (13)C nuclear magnetic resonance spectrometry, and comparison to authentic compounds and literature data. Neutral-pH ethyl acetate extracts from anthracene-incubated cells showed four metabolites, identified as cis-1,2-dihydroxy-1,2-dihydroanthracene, 6,7-benzocoumarin, 1-methoxy-2-hydroxyanthracene, and 9,10-anthraquinone. A novel anthracene ring fission product was isolated from acidified culture media and was identified as 3-(2-carboxyvinyl)naphthalene-2-carboxylic acid. 6,7-Benzocoumarin was also found in that extract. When Mycobacterium sp. strain PYR-1 was grown in the presence of phenanthrene, three neutral metabolites were identified as cis- and trans-9,10-dihydroxy-9,10-dihydrophenanthrene and cis-3,4-dihydroxy-3,4-dihydrophenanthrene. Phenanthrene ring fission products, isolated from acid extracts, were identified as 2,2'-diphenic acid, 1-hydroxynaphthoic acid, and phthalic acid. The data point to the existence, next to already known routes for both gram-negative and gram-positive bacteria, of alternative pathways that might be due to the presence of different dioxygenases or to a relaxed specificity of the same dioxygenase for initial attack on polycyclic aromatic hydrocarbons.

FIG. 1

Degradation (●) and mineralization (○) of anthracene (dashed line) and phenanthrene (solid line) by Mycobacterium sp. strain PYR-1.

FIG. 2

HPLC elution profile of metabolites produced during the growth of Mycobacterium sp. strain PYR-1 in the presence of phenanthrene and anthracene. (A) Ethyl acetate-extractable metabolites from phenanthrene-grown cultures. (B) Ethyl acetate-extractable metabolites from the acidified aqueous phase of phenanthrene-grown cultures. (C) Ethyl acetate-extractable metabolites from anthracene-grown cultures. (D) Ethyl acetate-extractable metabolites from the acidified aqueous phase of anthracene-grown cultures.

FIG. 3

Proposed pathways for the degradation of anthracene (A) and phenanthrene (B) by Mycobacterium sp. strain PYR-1.

FIG. 3

Proposed pathways for the degradation of anthracene (A) and phenanthrene (B) by Mycobacterium sp. strain PYR-1.