Characterization of a moderate thermophilic Nocardia species able to grow on polycyclic aromatic hydrocarbons

Our goal was the characterization of a new moderate thermophilic polycyclic aromatic hydrocarbon (PAH)-utilizing Nocardia strain. A thermophilic bacterium, strain TSH1, was isolated from a contaminated soil. The macroscopic and microscopic features fit well with the description of Nocardia species. The results of 16S rRNA gene analysis showed 100% match to the type strain of N. otitidiscaviarum DSM 43242(T). Strain TSH1 showed the same mycolic acid pattern as the type strain of N. otitidiscaviarum but its fatty acid profile did not permit identification to the species level. The carbon utilization profile of strain TSH1 was different from N. otitidiscaviarum. The results of hydrophobicity measurements showed that PAHs-grown cells were significantly more hydrophobic than LB-grown cells. Furthermore, biosurfactant production was detected during bacterial growth on different culture media. Strain TSH1 is capable of growing on a range of PAHs. When grown in PAHs-supplemented media, strain TSH1 showed a high affinity for the organic phase, suggesting that it can develop a hydrophobic surface. High cell surface hydrophobicity and capability of strain TSH1 to degrade different PAHs at 50 degrees C may make it an ideal candidate to treat PAH-contaminated desert soils.