MICROBIAL DIVERSITY AS A POSSIBLE SOLUTION FOR RESTORING A PAHS CONTAMINATED SOIL

The soil ecosystem is variable and complex and host a huge variety of microorganisms that by interacting with each other provide several ecosystem services. Due to the increase of industrial activities and to the combustion of fossil fuels and organic matter, the release of polyaromatic hydrocarbons (PAHs) threatens the health of natural ecosystems. Soil contamination by PAHs is an ever more severe issue that requires a sustainable solution, both in natural and anthropic environments. A wide range of microorganisms are capable of degrading these recalcitrant compounds. Thus, investigating and identifying the microbial communities inhabiting PAH-contaminated soils is crucial for designing appropriate remediation approaches. In this work, we investigated the microbial diversity of a formerly cultivated urban garden in Torino (Italy), mainly contaminated by Benzo(a)pyrene, Benzo(g,h,i)perylene, Fluoranthene, and Phenanthrene. Overall, 181 fungal isolates, mostly belonging to Ascomycota were retrieved and were affiliated to 38 genera and 66 species, including putative novel taxa. In addition, culturomics allowed the isolation of almost 200 bacterial strains, whose identification is currently ongoing. Thereafter, in order to select those strains capable of degrading PAHs, enrichment assays were conducted with each of the four target pollutants as sole carbon source. In parallel, metabarcoding analyses of both fungal and bacterial communities were employed to investigate the unculturable diversity. Unfortunately, there is another side of the coin: polluted soils can lead to the selection of antimicrobial resistant bacteria. Indeed, 18 species resistant to geneticin and penicillin/streptomycin were isolated in this study. The outcome of the currently ongoing assays will serve to evaluate the degradative potential of the isolated microorganisms, and to plan and develop remediation strategies, based on microbial consortia, for in situ applications.