Objective: The aim of this study is to identify a polycyclic aromatic hydrocarbons (PAHs)-degrading bacterium isolated from deep-sea hydrothermal environment, including its taxonomy, characteristics and mechanism involved in PAH degradation.
Methods: The phylogeny was studied by 16S rRNA gene clone, and the degradation rates against different PAHs were determined by GC-MS. Meanwhile, PAH-degrading gene cluster was cloned by the genomic Fosmid library construction; the function of the key degrading-gene expression was examined by RT-PCR and qPCR to observe gene expression in the response to different PAHs.
Results: A PAH-degrading strain TVG9-VII was isolated from the hydrothermal chimney sample of the Lau basin in Southwest Pacific Ocean. It showed 99.7% similarities with 16S rRNA gene of Novosphingobium indicum strain H25(T). The degradation rates of this strain against phenanthrene, fluoranthene and pyrene were 95.2%, 57.3% and 69.6% in 21 days, respectively. A gene cluster, containing PAHs initial dioxygenase genes pheA1a and pheA1b, was obtained from genomic fosmid library, with the insertion size of 12.522 kb. The gene pheA1a was enhanced by 4.2 folds in mRNA expression in presence of phenanthrene, but expression enhancement was not observed in other tested PAHs including naphthalene, pyrene and fluoranthene.
Conclusion: Strain TVG9-VII is isolated from deep-sea hydrothermal environment in genus Novosphingobium. It can degrade many kinds of PAHs, especially the high-weight-molecular PAHs.