Evolution of Functional Bacteria in a Polycyclic Aromatic Hydrocarbon (PAH)‐Degrading Bioreactor

ABSTRACT In this study a laboratory‐scale sequencing batch bioreactor was constructed, using phenanthrene/pyrene as the sole carbon‐source, to demonstrate the removal efficiencies of polycyclic aromatic hydrocarbons (PAHs) and the evolution process of a functional bacterial community. The removal rates were: COD, 51.4 to 76.3%; phenanthrene, 63.5 to 92.4%; and pyrene, 65.9 to 90.1%. Quantification analysis indicated that in sludge samples from the phenanthrene/pyrene degradation stage, the contents of 16S rRNA and ring‐hydroxylating dioxygenase genes of Gram‐positive and Gram‐negative bacteria were 10‐and 72‐, 102‐ and 1152‐, 31‐ and 905‐fold higher, respectively, than those in seed sludge samples. Clone sequencing and evolution analysis showed that genera Comamonas , Pseudomonas , and Mycobacterium were distributed across all samples and were significant PAH‐degrading populations, but some genera, such as Polaromonas and Nocardioides , were substantially enriched only when phenanthrene/pyrene was fed. Correspondingly, the functional genes nidA3 , phnAc , and ndoC2 were distributed across all samples, whereas nagAc , pdoA2 , and pdoA were enriched only when phenanthrene/pyrene was fed.