Occultifur mephitis f.A., sp. Nov. and other yeast species from hypoxic and elevated CO₂ mofette environments

An inventory of culturable yeasts from the soil and water of natural CO₂ springs (mofettes) in northeast Slovenia is presented. In mofettes, CO₂ of geological origin reaches the soil surface causing temporarily and spatially stable hypoxic environments in soil and water. In total, 142 yeast strains were isolated and identified from high CO₂ and control meadow soil, meadow ground-water, forest pond and stream water. All water locations showed below-ground CO₂ release. They were assigned to six basidiomycetous yeast genera (six species) and 11 ascomycetous genera (18 species). All ascomycetous yeasts, with the exception of Debaryomyces hansenii, were able to grow under elevated CO₂ and fermented glucose. Candida sophiae-reginae, Pichia fermentans and Candida vartiovaarae were the dominating species in meadow and forest high CO₂ exposed water. Meyerozyma guilliermondii and Wickerhamomyces anomalus predominated in high CO₂ exposed soils. Using high dilution plating of a mofette soil sample, four strains of an unknown basidiomycetous species were isolated and are here newly described as Occultifur mephitis based on molecular phylogenetic and phenotypic criteria. The type strain of Occultifur mephitis is EXF-6436^T[CBS 14611=PYCC 7049, LT594852 (D1/D2), KX929055 (ITS)]. An additional three isolated strains are EXF-6437 (LT594853, KX929056), EXF-6473 (LT594863, KX929057) and EXF-6482 (LT594867, KX929054), as well as a strain reported from previous studies isolated from a leaf of Cistus albidus in Portugal (CBS 10223=PYCC 6067), EU002842 (D1/D2), KY308183 (ITS).