Isolation and characterization of a bacterial strain Hydrogenophaga sp. PYR1 for anaerobic pyrene and benzo[a]pyrene biodegradation

A pyrene-degrading strain Hydrogenophaga sp. PYR1 was isolated from PAH-contaminated river sediments and found to be able to degrade high molecular weight-polycyclic aromatic hydrocarbons under both aerobic and anaerobic conditions. The strain was Gram-negative, rod-shaped, pale yellow and motile flagellum with rounded ends. Under aerobic conditions, 94% pyrene could be degraded by the strain PYR1 within 15 d at 28 °C, while the degradation of benzo[a]pyrene was not obvious. However, this strain could significantly degrade pyrene and even benzo[a]pyrene under iron-reducing anaerobic conditions. Through Fourier transform infrared spectroscopy and amino acids analysis, it was found that ferric citrate as the sole electron acceptor stimulated lipopeptide biosurfactant production by the strain during PAH degradation. The presence of lipopeptide biosurfactant facilitated benzo[a]pyrene degradation possibly through improving the bioavailability of benzo[a]pyrene. Furthermore, six intermediates formed under iron-reducing conditions were identified, and then a pathway for anaerobic benzo[a]pyrene degradation by this strain was proposed. It seemed that this bacterial isolate has great potential in the bioremediation of PAH-contaminated sediments.