Study of microbial diversity associated to Pistacia lentiscus, a metallophyte of Sardinian mining areas

Mine tailings represent a large-scale issue requiring the development of a sustainable remediation management plan with a multifactorial approach. In the Iglesiente region, past mining activities left severe contamination of Zn, Pb and Cd. Among bioremediation technologies, phytoremediation appears to be a promising strategy owing to the use of autochthonous plant species and their associated microorganisms naturally adapted to these harsh conditions. Among phytoremediation strategies, phytostabilization takes place at the root-substrate interface, where excluder-type metallophytes and their root-associated microorganisms reduce metal mobility and bioavailability. The effectiveness of this process largely depends on the structure and function of the rhizospheric microbiome. Therefore, the study of microbiome in rhizosphere and roots of native plants is crucial for the development of a successful remediation strategy. In this study, we investigated the rhizosphere and root microbiomes of Pistacia lentiscus, a metallophyte autochthonous plant species of Sardinian mining areas. Furthermore, the environmental context was analysed with a multifactorial approach to understand the most suitable application of phytoremediation in real field conditions. Sampling was conducted in three zones based on proximity to a mine tailing deposit: outside, at the border, and inside the dump. A comprehensive insight into soil communities was achieved by using diverse techniques. In this study we analysed: i) physico-chemical properties of mine substrates, ii) microbial activity by the dehydrogenase assay, iii) functional diversity patterns of microbial community with the BIOLOG system, iv) bacterial and fungal communities by high-throughput sequencing of ribosomal genes. Metals levels in the tailings showed a certain degree of spatial heterogeneity. Dehydrogenase activity showed a marked and statistically significant differences in the functional diversity of the rhizospheric microbial communities from the three different investigated areas. Analysis of microbial community by high-throughput sequencing allow us to understand how microbial communities were affected by environmental conditions and metals. Our results highlight the importance of plant-associated microbiomes in metal-contaminated environments and support their relevance for site-specific remediation strategies. This work has been developed within the framework of the project e.INS www.einsardinia.eu (Next Generation EU- PNRR-M4 C2 I1.5 CUP F53C22000430001).