Polycyclic aromatic hydrocarbon degradation by a Mycobacterium sp. in microcosms containing sediment and water from a pristine ecosystem.

Microcosm studies were conducted to evaluate the survival and performance of a recently discovered polycyclic aromatic hydrocarbon (PAH)-degrading Mycobacterium sp. when this organism was added to sediment and water from a pristine ecosystem. Microcosms inoculated with the Mycobacterium sp. showed enhanced mineralization, singly and as components in a mixture, of 2-methylnaphthalene, phenanthrene, pyrene, and benzo[alpha]pyrene. Studies utilizing pyrene as the sole added PAH showed that the Mycobacterium sp. survived in microcosms for 6 weeks both with and without preexposure to PAH and mineralized multiple doses of pyrene. Pyrene mineralization rates for sterilized microcosms inoculated with the Mycobacterium sp. showed that competition with indigenous microorganisms did not adversely affect survival of or pyrene degradation by the Mycobacterium sp. Pyrene mineralization by the Mycobacterium sp. was not enhanced by inorganic nutrient enrichment and was hindered by organic nutrient enrichment, which appeared to result from overgrowth of indigenous bacteria. This study demonstrates the versatility of the PAH-degrading Mycobacterium sp. and expands its potential applications to include the degradation of two-, three-, four-, and five-ringed PAHs in sediments.