Rapid mineralization of benzo[a]pyrene by a microbial consortium growing on diesel fuel

A microbial consortium which rapidly mineralized the environmentally persis tent pollutant benzo[a]pyrene was recovered from soil. The consortium comet abolically converted [7-C-14]benzo[a]pyrene to (CO2)-C-14 when it was grown on diesel fuel, and the extent of benzo[a]pyrene mineralization was depend ent on both diesel fuel and benzo[a]pyrene concentrations, Addition of dies el fuel at concentrations ranging from 0.007 to 0.2% (wt/vol) stimulated th e mineralization of 10 mg of benzo[a]pyrene per liter 33 to 65% during a 2- week incubation period. When the benzo[a]pyrene concentration was 10 to 100 mg liter(-1) and the diesel fuel concentration was 0.1% (wt/vol), an inocu lum containing 1 mg of cell protein per liter (small inoculum) resulted in mineralization of up to 17.2 mg of benzo[a]pyrene per liter in 16 days. Thi s corresponded to 35% of the added radiolabel when the concentration of ben zo[a]pyrene was 50 mg liter(-1). A radiocarbon mass balance analysis recove red 25% of the added benzo[a]pyrene solubilized in the culture suspension p rior to mineralization. Populations growing on diesel fuel most likely prom oted emulsification of benzo[a]pyrene through the production of surface-act ive compounds, The consortium was also analyzed by PCR-denaturing gradient gel electrophoresis of 16S rRNA gene fragments, and 12 dominant bands, repr esenting different sequence types, were detected during a 19-day incubation period. The onset of benzo[a]pyrene mineralization was compared to changes in the consortium community structure and was found to correlate with the emergence of at least four sequence types. DNA from 10 sequence types were successfully purified and sequenced, and that data revealed that eight of t he consortium members were related to the class Proteobacteria but that the consortium also included members which were related to the genera Mycobact erium and Sphingobacterium.