Opposite selection effects of nZVI and PAHs on bacterial community composition revealed by universal and sphingomonads-specific 16S rRNA primers.

Next-generation sequencing method employing the sphingomonads-specific and universal 16s rRNA primers were applied to analyze the response of soil bacterial community to continuous stress of nanoscale zero-valent iron (nZVI) and/or polycyclic aromatic hydrocarbons (PAHs) under suspended conditions. The group specific primer greatly improves taxonomic resolution, the overall OTU numbers increased from 12 by universal primer to 42 by sphingomonads-specific primer. It was found that nZVI and PAHs had opposite selection effects on bacterial community composition, furthermore, the abundance of Sphingopyxis was positively related to nZVI while negatively related to PAHs, whereas abundances of Sphingobium and Sphingosinicella were positively related to PAHs (p < 0.01). The improved taxonomic resolution helps identify the potential keystone taxa, which provides valuable information for future bioremediation technology such as synthetic microbiome.