Extremotolerant fungi in resinous soils: a unique diversity of generalists and specialized hydrocarbon degraders

Filamentous fungi are ubiquitous and constitute more than 75% of the soil biomass. Fungal diversity increasingly emerges as a key factor in soil ecosystem resilience against climate change and pollution, yet much of this diversity remains hidden and potentially in decline. While investigations have primarily focused on fungal tolerance to extreme physical conditions, such as temperature and salinity, chemically stressed environments remain underexplored reservoirs of novel fungal diversity. These habitats may harbor strains with significant biotechnological potential. This study tested the hypothesis that long-term contamination of soil with Pinus resin alters fungal diversity and promotes the growth of specialized fungal lineages enriched in hydrocarbon-degrading capabilities. We analyzed a resinous soil sample collected from an inactive resin processing site undisturbed for nearly 50 years. Initial physicochemical and microscopy analyses confirmed the presence of viable fungi despite extreme environmental constraints. High-throughput sequencing of fungal ITS2 regions revealed a fungal community composition highly distinct from adjacent forest soil, characterized by unusual taxonomic profiles and a high proportion of poorly classified or novel lineages. Functional inference and taxonomic analyses identified hydrocarbon-associated taxa including Sorocybe resinae (one of the most abundant OTUs) and Amorphotheca resinae (detected at low abundance). These fungi are known resinicolous and extremophilic species, illustrating the unique ecological adaptation of fungi within resin-rich, chemically stressful soils.