Identification of the belowground microbial community in a poplar-phytoremediation strategy of a multi-contaminated soil

Polychlorobiphenyls (PCBs) and heavy metals (HMs) due to their widely use in industrial applications in the past decades are the most common frequently soil contaminants worldwide, posing a risk for both ecosystem and human health.A poplar-assisted bioremediation strategy has been applied for more than four 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 shift in the structure and functioning of the belowground microbial community was also observed analysing both DNA and cDNA sequencing. A significant increase in bacterial genera belonging to Proteobacteria and able to degrade PCBs and resist to HMs were 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 showing the effectiveness of the poplar clone applied to stimulate the natural belowground microbial community to remove contaminants (phyto-assited bioremdiation), is a good example of a real case study of nature based solutions.