Endolithic fungal diversity is present in the unique phosphatized rocks of an environmentally extreme equatorial archipelago, revealed by DNA metabarcoding

We evaluated endolithic fungal diversity associated with rocks sampled at the polyextreme Brazilian São Pedro and São Paulo archipelago using a DNA amplicon metagenomics approach. We detected 808,547 fungal DNA reads grouped into 92 amplicon sequence variants (ASVs). The rocks sampled were geologically characterized as mylonitized peridotites, serpentinized peridotites, and carbonate-matrix sedimentary breccias. Ascomycota was the dominant phylum, followed by Basidiomycota, Mucoromycota, Mortierellomycota and Chytridiomycota. Hortaea werneckii, Cladosporium sp., Simplicillium sp., Blastobotrys serpentis, Penicillium sp., P. simplicissimum, Malassezia restricta, Ascomycota sp., Verrucariaceae sp., and Fungal sp. were the dominant assigned taxa. The endolithic assemblages displayed moderate to low diversity indices. Among the fungal community, only the dominant Fungal sp. occurred in all samples. The data obtained in our environmental DNA (eDNA) amplicon metagenomics approach suggest that the rocks of the isolated equatorial São Pedro and São Paulo archipelago host a complex fungal diversity, including taxa regarded to be cosmopolitan, extremophilic hypersaline and xerophilic, plant pathogens, and human/animal opportunistic pathogens. As eDNA studies do not confirm the presence of viable organisms or propagules, further research using culturing approaches is now required to develop strategies to recover these fungi for physiological, biogeochemical, genetic and potential biotechnological studies.