Three new genera of fungi from extremely acidic soils

Extremely acidic soils (pH < 3) harbour poorly diversified mycobiota that are very different from less acidic habitats. During investigations of the mycobiota from several highly acidic soils in the Czech Republic and a coastal site in the Antarctic Peninsula, a group of hyaline fungal isolates was obtained. Based on phenotype and nuclear ribosomal DNA sequences (ITS region, SSU, LSU), the isolates belonged to three phylogenetic lineages within two different classes, Sordariomycetes and Leotiomycetes (Pezizomycotina, Ascomycota). The first lineage is described here as a new genus and species Acidothrix acidophila gen. nov. et sp. nov. (Amplistromataceae, Sordariomycetes, Ascomycota). The most closely related species to this new clade are wood-inhabiting fungi. The isolates belonging to the second and the third lineages are also described as two new genera and species Acidea extrema gen. nov. et sp. nov. and Soosiella minima gen. nov. et sp. nov. (Helotiales, Leotiomycetes, Ascomycota). Their position and the relationships within Helotiales are discussed. Soosiella minima was acidotolerant, Acidothrix acidophila and Acidea extrema exhibited both acidotolerant and acidophilic characteristics. All the species were slightly halophilic. The adaptation of hyaline fungi from mesophilic lineages to highly acidic environments has been revealed. The association between highly acidic and Antarctic habitats is discussed.