Complementary spatial pattern of phenanthrene-degrading bacteria along a fine scale rhizosphere gradient. rhizosphere-sip

Rhizosphere is a critical interface for pollutant remediation in soil; degradation of organic pollutants non-linearly varied along a rhizosphere gradient. Association of the non-linearly variation and spatial pattern of degraders along rhizosphere gradient is, however, still unclear. This study investigated the phenanthrene degrading bacterial consortia in Phragmites australis rhizosphere using stable isotope probing. The relative abundance of Rhizobiales was higher in the 13C-labeled bacterial consortia, while the relative abundance of Flavobacteriales was higher in the unlabeled bacterial consortia. The high proportion of the 13C-labeled reads indicated that Rhizobiales, Rhodobacterales, Lactobacillales, Sphingomonadales, and Clostridiales had high degrading capability. The co-occurrence network suggested that the association number decreased with the degrading capability. The relative abundance of various taxa in the 13C-labeled bacterial consortia has opposite tendency along the rhizosphere gradient. The predicted metagenomes showed that the taxa inhibited near root surface degraded phenanthrene via dioxygenase pathway, while the taxa stimulated near root surface degraded phenanthrene via co-metabolism pathway. Overall, the complement between bacterial taxa with different degrading pathways leaded to the non-linear variation of degradation rates along rhizosphere gradient. These findings highlight that the spatial patterns in the rhizosphere gradient were opposite for taxa groups with different strategies in phenanthrene degradation.