Niche partition of phenanthrene-degrading bacteria along a Phragmites australis rhizosphere gradient

Abstract

The rhizosphere is a critical interface for pollutant remediation in soils. Association between biodegradation of organic pollutants and spatial pattern of degraders along the rhizosphere gradient is, however, still unclear. This study investigated the phenanthrene-degrading bacterial consortia in a Phragmites australis rhizosphere using DNA-stable isotope probing (DNA-SIP). The relative abundance of Sphingomonadales in the 13C-labeled consortia decreased with the distance from roots, suggesting that its contribution in phenanthrene degradation was decreased with the distance from roots. Conversely, the relative abundance of Rhizobiales, Rhodobacterales, Lactobacillales, and Enterobacteriales in 13C-labeled consortia increased with the distance from roots, suggesting that their contributions in phenanthrene degradation were increased with the distance from roots. The linkage numbers of bacterial species in the co-occurrence network increased with the percentages of 13C-labeled reads, suggesting the critical role of syntrophic interactions for phenanthrene degraders. These results suggest the niche partition of phenanthrene degraders, which leaded to the non-linear variation of phenanthrene degradation rates along the rhizosphere gradient. These findings will help us to better understand rhizo degradation of organic pollutants and optimize bioremediation technology by achieving a trade-off among different degraders.