Change of bacterial communities in sediments along Songhua River in Northeastern China after a nitrobenzene pollution event

More than 100 tons of nitrobenzene and related compounds were released into Songhua River due to the explosion of an aniline production factory in November, 2005. Sediment samples were taken from the heavily polluted drainage canal, one upstream and three downstream river sites. The change of bacterial community structures along the river was studied by denaturing gradient gel electrophoresis (DGGE) and cloning and sequencing of 16S rRNA genes with five clone libraries constructed and 101 sequences acquired representing 172 clones. Both DGGE profiles and sequences of 16S rRNA genes from clone libraries demonstrated that the contaminated drainage canal and three downstream river sites were similar in that all had Betaproteobacteria, mainly grouped into Comamonadaceae, as the dominant group of bacteria, and all had Firmicutes, primarily as Clostridium spp. These results suggest that these latter two groups of bacteria may play potential roles in degradation and detoxification of nitrobenzene in the present contaminated river environments.