Soil bacterial diversity and functionality are driven by plant species for enhancing polycyclic aromatic hydrocarbons dissipation in soils

Plant-microorganisms symbiosis has been widely used in developing strategies for the rhizoremediation of polycyclic aromatic hydrocarbon (PAHs) contaminated agricultural soils. However, understanding the potential mechanisms for using complex plant-microbe interactions to enhance rhizoremediation in contaminated soils is still limited. In this study, rhizosphere microbiomes were established by cultivating four types of cover crops for 15 months in a PAHs-contaminated field. The results showed that the PAHs removal rates were significantly higher in rhizosphere soils (55.2-82.3%) than the bare soils (20.5%). Of the four cover crops, the rhizosphere soils associated with the alfalfa and clover had higher removal rates for high molecular weight (HMW) PAHs (78.5-87.1%) than the grasses (39.0-46.2%). High-throughput sequencing analysis showed that bacterial community structure between the planted and bare soils, and among four cover crops rhizosphere soils were significantly different. The rhizosphere soils associated with the alfalfa and clover had more abundant degradation-related taxa. Correlation network analysis showed that bacterial communities with high removal rates have stronger interactions. Metagenome analysis indicated that the relative abundance of the key functional genes involved in PAHs degradation and nutrient metabolisms were significantly higher in rhizosphere soils, especially for alfalfa and clover. Overall, this study provides new insights for us to understand the mechanisms by different plants enhancing PAHs dissipation from the viewpoint of microbiology.