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The effect of polycyclic aromatic hydrocarbons on the degradation of benzo[ a ]pyrene by Mycobacterium sp. strain RJGII‐135
Author(s) -
McLellan Sandra L.,
Warshawsky David,
Shann Jodi R.
Publication year - 2002
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1002/etc.5620210205
Subject(s) - pyrene , phenanthrene , anthracene , chemistry , polycyclic aromatic hydrocarbon , strain (injury) , mycobacterium , stereochemistry , nuclear chemistry , organic chemistry , bacteria , biology , genetics , anatomy
Mycobacterium sp. strain RJGII‐135 is capable of degrading a wide range of polycyclic aromatic hydrocarbons (PAHs), including benzo[ a ]pyrene (B a P). In this study, critical aspects of degradation were investigated, including compound uptake, relative rates of PAH degradation, and the effects of co‐occurring PAH substrates on B a P degradation and mineralization to CO 2 . Mycobacterium sp. strain RJGII‐135 was capable of degrading phenanthrene, anthracene, and pyrene at a 10‐ to 20‐fold greater rate than benz[ a ]anthracene (B a A) and B a P. A significant amount of phenanthrene and pyrene, 30% and 10%, respectively, was completely mineralized, whereas less than 4% of anthracene, B a A, and B a P was mineralized. The PAH uptake assays demonstrated that high amounts of B a P and B a A, 81% and 75% of added compound, respectively, could be recovered from bacterial cell fractions after a 4‐h incubation compared with pyrene (61%), anthracene (53%), and phenanthrene (47%). The half‐saturation constant ( K m ) for pyrene was threefold lower for pyrene over B a P, suggesting that the degradation system in Mycobacterium sp. strain RJGII‐135 has a higher affinity for pyrene, reaching maximal degradative activity at lower concentrations. No hybridization to dioxygenase gene probes nah Ac, bph A1, or tol C1C2 was detected. Studies to investigate competition between different PAH substrates demonstrated that the rate of B a P metabolism was influenced by the presence of a second PAH substrate. The B a P metabolism was inhibited when coincubated with B a A, pyrene, and anthracene. Phenanthrene did not inhibit but enhanced B a P metabolism sixfold. These data suggest that induction effects of components of complex mixtures may be as important as competitive metabolism when assessing the ability of bacteria to effectively degrade high‐molecular‐weight PAHs in the environment.