Isolation and Characterization of a Mycobacterium Species Capable of Degrading Three- and Four-Ring Aromatic and Aliphatic Hydrocarbons

Mycobacterium sp. strain CH1 was isolated from polycyclic aromatic hydrocarbon (PAH)-contaminated freshwater sediments and identified by analysis of 16S rDNA sequences. Strain CH1 was capable of mineralizing three- and four-ring PAHs including phenanthrene, pyrene, and fluoranthene. In addition, strain CH1 could utilize phenanthrene or pyrene as a sole carbon and energy source. A lag phase of at least 3 days was observed during pyrene mineralization. This lag phase decreased to less than 1 day when strain CH1 was grown in the presence of phenanthrene or fluoranthene. Strain CH1 also was capable of using a wide range of alkanes as sole carbon and energy sources. No DNA hybridization was detected with thenahAc gene probe, indicating that enzymes involved in PAH metabolism are not related to the well-characterized naphthalene dioxygenase gene. DNA hybridization was not detected when thealkB gene fromPseudomonas oleovorans was used under high-stringency conditions. However, there was slight but detectable hybridization under low-stringency conditions. This suggests a distant relationship between genes involved in alkane oxidation.