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