Species Diversity and Polymorphism in theExophiala spiniferaClade Containing Opportunistic Black Yeast-Like Fungi

Abstract

A monophyletic group of black yeast-like fungi containing opportunistic pathogens around Exophiala spinifera is analyzed using sequences of the small-subunit (SSU) and internal transcribed spacer (ITS) domains of ribosomal DNA. The group contains yeast-like and annellidic species (anamorph genus Exophiala) in addition to sympodial taxa (anamorph genera Ramichloridium and Rhinocladiella). The new species Exophiala oligosperma, Ramichloridium basitonum, and Rhinocladiella similis are introduced and compared with their morphologically similar counterparts at larger phylogenetic distances outside the E. spinifera clade. Exophiala jeanselmei is redefined. New combinations are proposed in Exophiala: Exophiala exophialae for Phaeococcomyces exophialae and Exophiala heteromorpha for E. jeanselmei var. heteromorpha.A significant portion of the species of black yeasts and their filamentous relatives, anamorphs of members of the order Chaetothyriales, are regularly encountered as causative agents of human mycoses (9). They exhibit a relatively high degree of molecular diversity (10) but seem to possess common factors which enable them to invade the human host, resulting in a bewildering diversity of mycoses, such as chromoblastomycosis, mycetoma, brain infection, and other types of phaeohyphomycosis (9). In harboring a wide array of clinically relevant species, the Chaetothyriales are unique in the fungal kingdom: they are only matched by the Onygenales, the order containing the dermatophytes and the dimorphic pathogens. Understanding the species diversity of the Chaetothyriales and their specific ecology is of considerable medical relevance.This wide species spectrum is only poorly understood, as until recently insufficient markers were available for a reliable distinction of taxa. Morphology is poorly developed in these fungi, and when present, very similar microscopic structures can be expressed in phylogenetically remote species (15). Sequencing studies of the ribosomal operon have shown that this gene can be successfully applied to species delimitation and identification. A large number of new taxa have to be introduced; many of these have a pathogenic potential.In an extended 18S ribosomal DNA (rDNA) sequencing study of black yeasts and their allies, Haase et al. (15) showed that the phylogenetic tree of the Chaetothyriales is poorly resolved, which indicates a radiation of taxa within a relatively short evolutionary period. All anamorph genera concerned proved to be polyphyletic (15); the morphological entities were nevertheless maintained for practical reasons. The single teleomorph genus in the order, Capronia, was found throughout the tree but appeared to have limited clinical relevance.

New and interesting chaetothyrialean fungi from Spain

“…However, they can be distinguished by conidial morphology and size, i.e. subglobose to ellipsoidal and 2.5-3.8 × 1.8-2.5 μm in R. anceps, short-cylindrical and 3.7-5.5 × 1.2-1.8 μm in R. atrovirens, guttuliform to clavate and 3.5-4.5 × 2.2 μm in R. basitona, and cylindrical, 4-7 × 1.5 μm in R. similis (de Hoog and Hermanides-Nijhof 1977;de Hoog et al 2003). Furthermore, the yeast cells that are often produced in culture by R. anceps, R. atrovirens and R. similis (de Hoog and Hermanides-Nijhof 1977;de Hoog et al 2000de Hoog et al , 2003 were not observed in R. amoena.…”

Metagenomic analysis of soil fungal communities on Ulleungdo and Dokdo Islands

“…The family Herpotrichiellaceae of the class Eurotiomycetes of Ascomycota was present at high levels only in the Dongdo sample, whereas the family Trichocomaceae comprised greater than 1.0% of all families detected in the Dongdo and Seodo samples. Members of Herpotrichiellaceae have been characterized as human pathogens (de Hoog et al, 2003;Haase et al, 1999), while members of Trichocomaceae maintain saprophytic, pathogenic, and/or endophytic characteristics (da Costa et al, 1998;Khan et al, 2008;Samson et al, 2004;Valdez et al, 2006). The families Clavicipitaceae and Hypocreaceae of the class Sordariomycetes of Ascomycota were slightly more abundant in the Dongdo sample than in the Ulleungdo Fungal classes with a relative abundance greater than 1% in at least one of the three samples are shown.…”

Exophiala crusticola anam. nov. (affinity Herpotrichiellaceae), a novel black yeast from biological soil crusts in the Western United States

“…The Dictionary of Fungi (Kirk et al, 2001) cites twelve species in the genus Exophiala; however, additional species have been described more recently (e.g. de Hoog et al, 2003). Some species of the genus Exophiala are known as occasional opportunistic human pathogens (de Hoog et al, 2003;Haase et al, 1999).…”

“…However, the use of nuclear ribosomal RNA (nrRNA) gene sequence data has facilitated identification and classification of these organisms (see Spatafora et al, 1995;Untereiner & Naveau, 1999;de Hoog et al, 2003). The family is represented by the teleomorph genus Capronia and the anamorphic genera Cladophialophora, Exophiala, Fonsecaea, Phaeococcomyces, Phialophora, Ramichloridium and Rhinocladiella (Untereiner & Naveau, 1999).…”

“…de Hoog et al, 2003). Some species of the genus Exophiala are known as occasional opportunistic human pathogens (de Hoog et al, 2003;Haase et al, 1999).…”