Yeasts vectored by migratory birds collected in the Mediterranean island of Ustica and description of Phaffomyces usticensis f.a. sp. nov., a new species related to the cactus ecoclade.

Nine yeast species belonging to genera Candida, Cryptococcus, Phaffomyces, Rhodotorula and Wickerhamomyces, and one species of Aureobasidium genus were isolated from the cloaca of migratory birds. Candida glabrata and C. inconspicua were the species most frequently isolated and Wickerhamomyces sylviae, which has recently been described as a new species isolated from bird cloaca, was again found. The majority of isolates showed the ability to grow up to 40 °C and/or at pH 3.0, two environmental conditions typical of the digestive tract of birds. The phylogenetic analysis of the D1/D2 domain of 26S rRNA gene placed the cultures of Phaffomyces in a new lineage that differed from the closest species, P. opuntiae, by 13 nucleotide substitutions. The new species was able to grow at 40 °C and at pH 2.5, which suggests a possible adaptation to the bird cloaca. Moreover, the ability to grow in the presence of digitonin at pH 3.7 and the assimilation of ethyl acetate indicates a potential cactophilic origin. For the first time, the presence of yeasts belonging to the Phaffomyces clade in Europe and also in non-cactus environments is reported. The new species is formally described as P. usticensis sp. nov. (PYCC 6346T = CBS 12958T).