Complete and integrated pyrene degradation pathway in Mycobacterium vanbaalenii PYR-1 based on systems biology

Mycobacterium vanbaalenii PYR-1 was the first bacterium isolated by virtue of its ability to metabolize the high-molecular-weight polycyclic aromatic hydrocarbon (PAH) pyrene. We used metabolic, genomic, and proteomic approaches in this investigation to construct a complete and integrated pyrene degradation pathway for M. vanbaalenii PYR-1. Genome sequence analyses identified genes involved in the pyrene degradation pathway that we have proposed for this bacterium. To identify proteins involved in the degradation, we conducted a proteome analysis of cells exposed to pyrene using one-dimensional gel electrophoresis in combination with liquid chromatography-tandem mass spectrometry. Database searching performed with the M. vanbaalenii PYR-1 genome resulted in identification of 1,028 proteins with a protein false discovery rate of <1%. Based on both genomic and proteomic data, we identified 27 enzymes necessary for constructing a complete pathway for pyrene degradation. Our analyses indicate that this bacterium degrades pyrene to central intermediates through o-phthalate and the beta-ketoadipate pathway. Proteomic analysis also revealed that 18 enzymes in the pathway were upregulated more than twofold, as indicated by peptide counting when the organism was grown with pyrene; three copies of the terminal subunits of ring-hydroxylating oxygenase (NidAB2, MvanDraft_0817/0818, and PhtAaAb), dihydrodiol dehydrogenase (MvanDraft_0815), and ring cleavage dioxygenase (MvanDraft_3242) were detected only in pyrene-grown cells. The results presented here provide a comprehensive picture of pyrene metabolism in M. vanbaalenii PYR-1 and a useful framework for understanding cellular processes involved in PAH degradation.