Cyphellophora and its relatives in Phialophora: biodiversity and possible role in human infection

Cyphellophora is a genus of black yeast-like fungi characterised by having simple phialides with multiseptate, curved conidia. Judging from SSU and LSU data, Cyphellophora was found to be located in a well-supported clade within the Chaetothyriales comprising a number of species occurring on human skin and nail. Cyphellophora is phylogenetically close to Phialophora europaea, P. reptans and P. oxyspora, though morphologically these species produce single-celled phialoconidia rather than multiseptate ones. Pseudomicrodochium suttonii and P. fusarioides have dark colonies and phylogenetically fit in with Cyphellophora; the type species of Pseudomicrodochium, P. aciculare, has similar, septate conidia but has a hyaline thallus. In the present study, multilocus phylogenetic analyses were combined with morphology and physiology. Sequences of the internal transcribed spacer region, the DNA dependent RNA polymerase II largest subunit and the partial beta tubulin gene were analysed for a set of 30 strains. Two novel species, Cyphellophora pauciseptata and Phialophora ambigua were discovered. Cyphellophora eucalypti was reduced to synonymy of C. guyanensis. The role of the studied fungi between colonization and infection of human skin was discussed. Putative virulence factors for these black yeast-like fungi were hypothesized to be the ability to assimilate monoaromatic hydrocarbons, to produce melanin pigments, and to tolerate the temperature of epidermal human skin.