Fungalpedia – Note 3313, Atractiellomycetes
Atractiellomycetes R. Bauer, Begerow, J.P. Samp., M. Weiß & Oberw., Mycol. Progr. 5(1): 45 (2006).
Citation when using this data: Wijayawardene NN et al. 2024 – Fungalpedia.
Index Fungorum, Faceoffungi, MycoBank, GenBank.
Classification: Pucciniomycotina, Basidiomycota, Dikarya, Fungi.
Atractiellomycetes is a heterogenous class of which the representatives are only known from filamentous morphs, yeast budding is not known from this class. At the ultrastructural level, Atractiellomycetes are characterised by the presence of symplechosomes. These structures were described as stacked plate-like cisternae derived from the endoplasmatic reticulum, interconnected by hexagonally arranged filaments, and connected to mitochondria, but their origin and function remain unknown (Bauer and Oberwinkler 1991). Symplechosomes are synapomorphic for this class, but only a few species were investigated for their ultrastructural properties. Septal pores are complex and are associated with either microbodies or atractosomes (Bauer et al. 2006).
Atractiellomycetes comprise the order Atractiellales, the families Atractogloeaceae, Hoehnelomycetaceae and Phleogenaceae, ten genera, and more than 60 known species (Aime et al. 2018; Begerow et al. 2018; Schoutteten et al. 2018; Spirin et al. 2018; Cao et al. 2021).
The documented diversity of basidiomata in this class is high, with resupinate (Bourdotigloea, Helicogloea, Saccosoma), stilboid (Atractiella, Phleogena) and pycnidioid (Basidiopycnis, Proceropycnis) structrures. Basidia are transversally septate, contain laterally attached probasidia for karyogamy (Bourdotigloea, Helicogloea, and Saccosoma), and usually produce ballistospores (Baker 1936). The formation of statismospores is known from Atractogloea and Phleogena (Oberwinkler and Bandoni 1982). Some Atractiellomycetes are known from a teleomorphic and an anamorphic morph, of which the anamorps were formerly assigned to the genera Hobsonia, Infundibura, Leucogloea, and Pleurocolla (Kirschner 2004; Spirin et al. 2018). Some species are known exclusively from the anamorph, e.g. Proceropycnis pinicola (Oberwinkler et al. 2006).
Life modes and distribution: Atractiellomycetes have a worldwide distribution, covering Northern temperate and tropical /sub-tropical regions. Members of the class usually produce inconspicuous basidiomata or conidiomata, often on woody or herbaceous materials, sometimes overgrowing other fungi (Bauer et al. 2006; Aime et al. 2018, Spirin et al. 2018). Most Atractiellomycetes are considered saprobic, associated with decaying vegetation, or with bark beetle galleries in decaying conifer logs (Bauer et al. 2006; Oberwinkler et al. 2006). However, recent studies indicated that members of this class might be associated with plant roots and may be mycorrhizal or endorrhizal (Kottke et al. 2010; Bonito et al. 2017). One species is reportedly involved in in orchid mycorrhiza (Kottke et al. 2010), Atractiella rhizophila and Proceropycnis hameedii were found to be endophytes of Populus roots, and Atractidochium hillariae was recovered as an endophyte of Pinus taeda needles (Bonito et al. 2017; Aime et al. 2018).
Note: Most species in Atractiellomycetes are known from one or a few collections only, and DNA sequence data is often limited to ribosomal markers, or completely lacking (Schoutteten et al. 2018; Cao et al. 2021). Also, only a few cultures are available of Artactiellymycetes, and spore germination often occurs through the formation of microconidia (Bauer et al. 2006). Spirin et al. (2018) performed a taxonomic study on the resupinate, corticioid members of the Atractiellomycetes, focussing on the species formerly assigned to Helicogloea and Saccoblastia. He delineated three genera based on combined phylogenetic and morphological characters. Helicogloea spp. are characterised by efibulate hyphae and the absence of cystidia, Bourdotigloea spp. are characterised by efibulate hyphae and the presence of cystidia, and Saccosoma spp. are characterised by clamped hyphae and the absence of cystidia. However, the current sampling remains low, and sequencing of more well-studied material is necessary to further test and refine the proposed species delimitation in this group (Malysheva et al. 2020).
Type order: Atractiellales Oberw. & Bandoni, Can. J. Bot. 60(9): 1740 (1982).
Type family: Atractiellaceae R.T. Moore, Mycotaxon 59: 8 (1996).
Type genus : Atractiella Sacc., Syll. fung. (Abellini) 4: 578 (1886).
Type species : Atractiella brunaudiana (Sacc.) Sacc., Syll. fung. (Abellini) 4: 579 (1886).
Other accepted species: Species Fungorum – search Atractiellomycetes.
References
Begerow D, McTaggart A, Agerer R. 2018 – 1/3 Basidiomycota and Entorrhizomycota In: Frey, W. (Ed.) A. Engler’s Syllabus der Pflanzenfamilien. Germany: Bontraeger Science Publishers.
Kirschner R. 2004 – Sporodochial anamorphs of species of Helicogloea. Frontiers in basidiomycote mycology:165–178.
Entry by
Nalin N. Wijayawardene, Center for Yunnan Plateau Biological Resources Protection and Utilization, College of Biological Resource and Food Engineering, Qujing Normal University, Qujing, Yunnan 655011, P.R. China, Tropical Microbiology Research Foundation, 96/N/10, Meemanagoda Road, 10230 Pannipitiya, Sri Lanka, Department of Bioprocess Technology, Faculty of Technology, Rajarata University, Sri Lanka
Published online 2 October 2026