Pyrene Degradation by Mycobacterium gilvum : Metabolites and Proteins Involved

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are toxic organic pollutants and omnipresent in the aquatic and terrestrial ecosystems. A high-efficient pyrene-degrading strain CP13 was isolated from activated sludge and identified as Mycobacterium gilvum based on the analysis of 16S rRNA gene sequence. More than 95% of pyrene (50 mg L⁻¹) was removed by CP13 within 7 days under the alkaline condition. Pyrene metabolites, including 4-phenanthrenecarboxylic acid, 4-phenanthrenol, 1-naphthol, and phthalic acid, were detected and characterized by GC-MS. Results suggested that pyrene was initially attacked at positions C-4 and C-5, then followed by ortho cleavage, and further degraded following the phthalate metabolic pathway. Analysis of pyrene-induced proteins showed that the extradiol dioxygenase, a key enzyme involved in pyrene degradation, was highly up-regulated in pH 9 incubation condition, which illustrated the high efficiency of CP13 under alkaline environment. The present study demonstrated that the isolated bacterial strain CP13 is a good candidate for bioremediation of alkaline PAH-contaminated sites.

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