Diversity and novel lineages of black yeasts in Chaetothyriales from freshwater sediments in Spain

Abstract

Black yeasts comprise a group of Ascomycota of the order Chaetothyriales with highly variable morphology, a great diversity of ecological niches and life cycles. Despite the ubiquity of these fungi, their diversity in freshwater sediments is still poorly understood. During a survey of culturable Ascomycota from river and stream sediments in various sampling sites in Spain, we obtained 47 isolates of black yeasts by using potato dextrose agar supplemented with cycloheximide. A preliminary morphological study and sequence analyses of the internal transcribed spacer region (ITS) and the large subunit (LSU) of the nuclear rDNA revealed that most of the isolates belonged to the family Herpotrichiellaceae. We have confidently identified 30 isolates representing the following species: Capronia pulcherrima, Cladophialophora emmonsii, Exophiala equina, Exophiala pisciphila, Exophiala radicis, and Phialophora americana. However, we encountered difficulty in assigning 17 cultures to any known species within Chaetothyriales. Combining phenotypic and multi-locus phylogenetic analyses based on the ITS, LSU, β-tubulin (tub2) and translation elongation factor 1-α (tef1-α) gene markers, we propose the new genus Aciculomyces in the Herpotrichiellaceae to accommodate the novel species Aciculomyces restrictus. Other novel species in this family include Cladophialophora denticulata, Cladophialophora heterospora, Cladophialophora irregularis, Exophiala candelabrata, Exophiala dehoogii, Exophiala ramosa, Exophiala verticillata and Phialophora submersa. The new species Cyphellophora spiralis, closely related to Cyphellophora suttonii, is described, and the phylogeny of the genus Anthopsis in the family Cyphellophoraceae is discussed. By utilizing these four markers, we were able to strengthen the phylogenetic resolution and provide more robust taxonomic assessments within the studied group. Our findings indicate that freshwater sediments may serve as a reservoir for intriguing black yeasts, which warrant further investigation to address gaps in phylogenetic relationships, particularly within Herpotrichiellaceae.

Sunken Riches: Ascomycete Diversity in the Western Mediterranean Coast through Direct Plating and Flocculation, and Description of Four New Taxa

“…The strains that could represent potential unknown fungi were further analyzed under a consolidated species concept, combining morphological and phylogenetic data [44]. Alignments were constructed, including the sequences with the closest percentage of identity from the BLAST search and sequences from the most recent phylogenetic studies of the respective groups, namely Exophiala [45], Nigrocephalum [46], Queenslandipenidiella [44], and the family Schizotheciaceae [47,48]. Sequences were aligned using the ClustalW algorithm [49] in MEGA (Molecular Evolutionary Genetics Analysis) software v. 6.0 [50] and refined with MUSCLE [51] or adjusted manually as needed.…”

“…Sequences were aligned using the ClustalW algorithm [49] in MEGA (Molecular Evolutionary Genetics Analysis) software v. 6.0 [50] and refined with MUSCLE [51] or adjusted manually as needed. The analyses included more than one genetic region based on the previous phylogenies of each group [44][45][46][47][48]. Each region was aligned individually before being combined into a single dataset.…”

“…Minimum 5 Notes. The genus Exophiala represents a polyphyletic group in the family Herpotrichiellaceae, where E. littoralis is phylogenetically placed in the so-called jeanselmeiclade [45,60]. This species is morphologically similar to other species of this clade, such as E. hongkongensis, E. jeanselmei, E. nishimurae, E. oligosperma, and E. pseudooligosperma, by the production of cylindrical conidiogenous cells (Figure 5; Refs.…”

“…However, the production of claviform conidia with thick and truncate bases, the absence of budding Notes. The genus Exophiala represents a polyphyletic group in the family Herpotrichiellaceae, where E. littoralis is phylogenetically placed in the so-called jeanselmei-clade [45,60]. This species is morphologically similar to other species of this clade, such as E. hongkongensis, E. jeanselmei, E. nishimurae, E. oligosperma, and E. pseudooligosperma, by the production of cylindrical conidiogenous cells (Figure 5; Refs.…”

Exophiala amphawaensis sp. nov., a novel black yeast isolated from the gut of amphipods in Thailand

“…In the MycoBank database (https://www.mycobank.org/; December 2023), 70 species of the genus Exophiala have been recognised. Later, some species of the genus Exophiala were reassigned to the other genera like Hortaea and Neophaeococcomyces [9,10], while a few novel species have been described as members of the genus Exophiala [11][12][13].…”