Characterization of pyrene degradation by halophilic Thalassospira sp. strain TSL5-1 isolated from the coastal soil of Yellow Sea, China

Abstract

High molecular weight polycyclic aromatic hydrocarbons (HMW-PAHs) are more persistent and less bioavailable because of their poorer solubility in saline environments. In this study, a new halophilic bacterium capable of degrading various HMW-PAHs was isolated from the coastal soil of Yellow Sea, China. It was identified as Thalassospira sp. strain TSL5-1 based on 16S rRNA gene sequence analysis and biochemical tests. Influences of salinity, pH and additional nutrients on pyrene degradation by TSL5-1 were investigated. The pyrene degradation could occur at salinity ranging from 0.5% to 19.5%, with optimal value kept between 3.5% and 5%. The degradation activity was affected greatly by pH fluctuation. Yeast could efficiently promote pyrene removal while peptone had the opposite effect. GC–MS analysis revealed that the pyrene was degraded to generate a series of intermediates such as phenanthrene-4-carboxylic acid methyl ester, 2-hydroxy-2-H-benzo[h]chromene-2-carboxylic acid, 2-carboxylbenzaldehyde, phthalic acid and salicylic acid. Particularly, identification of phthalic acid and salicylic acid showed that phthalate and salicylic acid routes were simultaneously contained in the pyrene degradation, which was remarkably different from those for other pyrene-degraders. To our knowledge, it was the first time to propose a metabolic pathway of pyrene degradation by Thalassospira strains.