Different phenanthrene-degrading bacteria cultured by in situ soil substrate membrane system and traditional cultivation

Polycyclic aromatic hydrocarbons (PAHs) constitute a large, diverse group of organic compounds that commonly have detrimental biological effects that pose a great environmental threat. Hence, development of isolation and culture techniques for PAH-degrading bacteria is necessary. In this study, a variety of phenanthrene-degrading bacteria were enriched and isolated using an in situ soil substrate membrane system (SSMS) and a traditional cultivation method with phenanthrene as the sole carbon source. In the traditional method, the major species of phenanthrene-degrading bacteria found was Pseudomonas (Gammaproteobacteria). By contrast, the major phenanthrene-degrading bacteria observed using SSMS were Sphingomonas (Alphaproteobacteria). Phenanthrene utilization by bacteria with SSMS was higher than traditional cultivation method. High throughput functional microarray, Geochip, and polymerase chain reaction-denaturing gradient gel electrophoresis were used to characterize the response of soil bacterial communities upon addition of phenanthrene. Results indicated that members of the class Alphaproteobacteria were the dominant bacteria in phenanthrene-contaminated soils, and their characteristic phenanthrene-degrading genes have important role in degradation of contaminants. Sphingomonas was isolated using SSMS and found to be capable of adapting to nutrient-poor environments by utilizing a variety of substrates. The SSMS method is more suitable for the growth of Sphingomonas in simulated environmental conditions.