Microbial degradation of pyrene and characterization of a metabolite

We report the degradation of pyrene by microorganisms present in sea water and sediment samples that were obtained from Kitimat Arm, BC, Canada, an environment that is highly contaminated by polycyclic aromatic hydrocarbons because of nearby aluminum smelting activity. The utilization of pyrene as sole carbon source by the microorganisms is demonstrated by monitoring the disappearance of pyrene and the production of its metabolite in the cultures. Pyrene (10 μg) is degraded to an undetectable level after 120 h of incubation with 0.5 ml of the enriched culture and 10 ml of mineral salt medium. The extent of mineralization is also assessed by determining the radioactivity of the 14CO2 produced from the cultures containing 14C-labeled pyrene: up to 65% of the pyrene is mineralized after 12 days of incubation. A metabolite that accumulates in the pyrene degradation cultures can be isolated. This metabolite is identified as cis-dihydrobiol pyrene, an initial ring oxidation product, on the basis of its chromatographic behavior, absorption spectrum, fluorescence excitation and emission spectra, and mass spectra.