The effect of polycyclic aromatic hydrocarbon contamination on distribution of the Sphingomonas community in the Shenfu irrigation area of Northeast China

Information about the diversity and community structure of indigenous Sphingomonas communities in natural environments is lacking. In this study, denaturing gradient gel electrophoresis (DGGE) was used to investigate Sphingomonas communities at nine selected sites from the up-, mid- and downstream regions of a wastewater channel, which once flowed with sewage containing high concentrations of polycyclic aromatic hydrocarbons (PAHs). From each region, three samples from channel sediment, rice soil and corn soil were collected. Sediment sites had significantly higher PAH contamination, followed by rice sites and corn sites. In addition, upstream sites had higher PAH accumulation, followed by mid- and downstream sites. For each sample type (sediment, rice and corn soils), the Shannon diversity indices of the Sphingomonas community increased slightly with increasing PAH contamination. Upstream sites had obviously higher diversity than mid- and downstream sites. Both cluster analysis and canonical correspondence analysis indicated that the Sphingomonas community was clearly different among sediment, rice and corn soils. Besides, the Sphingomonas community was affected by different PAH compounds in sediment, rice and corn sites. The Sphingomonas community might degrade mainly benzo[b]fluoranthene, fluorene and fluoranthene in sediment sites by co-metabolism, but degraded mainly pyrene and phenanthrene in corn and rice sites, which provides some suggestions for pollution remediation.