Basidioascus and Geminibasidium: a new lineage of heat resistant and xerotolerant basidiomycetes

Nguyen, H.D.T., Nickerson, N.L., and Seifert, K.A. (2013). "Basidioascus and Geminibasidium: a new lineage of heat resistant and xerotolerant basidiomycetes", Mycologia, 105(5), pp. 1231-1250. doi : 10.3852/12-351  Access to full text


Using a heat treatment method, two genera of heat resistant and xerotolerant basidiomycetes were isolated from soil samples. These two genera, Basidioascus and Geminibasidium gen. nov., are morphologically similar and phylogenetically related. The genus Basidioascus was originally described as an ascomycete but the structures originally interpreted as single-spored asci appear to represent basidiospores. Morphologically, both genera are characterized by the lack of a fruiting body, conspicuously granular and deciduous basidia with a unique basal lateral projection, and apparently double walled basidiospores. The basidia, rather than the basidiospores, are forcibly discharged in Basidioascus species but not in Geminibasidium species. In Geminibasidium species, a putative basidium arises from a primary cell. These are novel forms of basidial ontogenesis previously unseen in basidiomycetes. The rDNA (SSU+5.8S+LSU) Bayesian phylogenetic analysis suggests that these fungi are distantly related to Wallemia, another xerotolerant basidiomycete genus commonly found in indoor air dust, dried foods and natural hypersaline environments. Given the physiological similarity and phylogenetic relationships, Basidioascus and Geminibasidium are classified in a new order, Geminibasidiales, and are taxonomically assigned to the class Wallemiomycetes. Based on morphological observations and molecular phylogeny of the internal transcribed spacer (ITS), two species of Basidioascus (B. undulatus and B. magus sp. nov.) and two species of Geminibasidium (G. donsium sp. nov. and G. hirsutum sp. nov.) are described. A key to these species is provided using micromorphological and cultural characters.

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