Characterization of the belowground nicrobial community in a poplar-phytoremediation strategy of a multi-contaminated soil

Due to their widespread use in industrial applications in recent decades, Polychlorobiphenyls (PCBs) and heavy metals (HMs) are the most common soil contaminants worldwide, posing a risk for both ecosystems and human health. In this study, a poplar-assisted bioremediation strategy has been applied for more than 4 years to a historically contaminated area (PCBs and HMs) in Southern Italy using the Monviso poplar clone. This clone was effective in promoting a decrease in all contaminants and an increase in soil quality in terms of organic carbon and microbial abundance. Moreover, a significant shift in the structure and predicted function of the belowground microbial community was also observed when analyzing both DNA and cDNA sequencing data. In fact, an increase in bacterial genera belonging to Proteobacteria able to degrade PCBs and resist HMs was observed. Moreover, the functional profiling of the microbial community predicted by PICRUSt2 made it possible to identify several genes associated with PCB transformation (e.g., bphAa, bphAb, bphB, bphC), response to HM oxidative stress (e.g., catalase, superoxide reductase, peroxidase) and HM uptake and expulsion (e.g., ABC transporters). This work demonstrated the effectiveness of the poplar clone Monviso in stimulating the natural belowground microbial community to remove contaminants and improve the overall soil quality. It is a practical example of a nature based solution involving synergic interactions between plants and the belowground microbial community.This research was performed for the Project “GREEN SOLUTIONS – Biorimedio fitoassistito: una strategia verde per il recupero di aree contaminate e la valorizzazione di biomassa” http://www.soluzioniverdi.eu/wordpress funded by Apulia Region (Italy) in the framework of INNONETWORK – POR PUGLIA FESR-FSE 2014-2020, N. Q3ITQH5. We declare that Apulia Region did not have any role in the design of the study, sample collection, analysis, interpretation of data, and in writing the manuscript