Fungalpedia – Note 3295, Pichiomycetes
Pichiomycetes M. Groenew., Hittinger, Opulente & A. Rokas, Stud. Mycol. 105: 11 (2023).
Citation when using this data: Wijayawardene NN et al. 2024 – Fungalpedia.
Index Fungorum, Faceoffungi, MycoBank, GenBank, Fig 1h-m.
Classification: Saccharomycotina, Ascomycota, Dikarya, Fungi.
Notes: Pichiomycetes was introduced as one of six new classes to classify yeasts of the subphylum Saccharomycotina according to evolutionary divergence based on the analysis of genomic data (Groenewald et al. 2023). The diagnosis of Pichiomycetes was provided as a class-specific orthologous group of proteins. For more details, see the entry on Saccharomycetes. Following the nomenclatural requirement to use a single name for a single taxon, the genus Candida, originally used to group morphologically indistinguishable anascosporogenous yeast species, is to be reduced to a group typified by C. tropicalis and situated in the Pichiomycetes (Daniel et al. 2014). However, in the understanding that conclusive phylogenetic inference necessitates complete taxon sampling and genomic data, Candida species outside the C. tropicalis group and outside of Pichiomycetes still await their reclassification.
Members of Pichiomycetes are significant economically and ecologically, clinically and industrially (see Tables 12, 13, and 14 respectively for examples; Wijayawardene NN et al. 2024).
According to Groenewald et al. (2023) the class comprises the three orders Alaninales, Pichiales, Serinales, accommodating five families and 41 genera. The genus Babjeviella represents a highly divergent lineage in the class and was not assigned to a family.
Type order: Pichiales M. Groenew., Hittinger, Opulente & A. Rokas, Stud. Mycol. 105: 12 (2023).
Type family: Pichiaceae M. Groenew., Hittinger, Opulente & A. Rokas, Stud. Mycol. 105: 12 (2023).
Type genus: Pichia E.C. Hansen, Centralbl. Bakteriol. Parasitenk., 2. Abth. 12: 538. (1904).
Type species: Pichia membranifaciens (E.C. Hansen) E.C. Hansen, Centralbl. Bakteriol. Parasitenk., 2. Abth. 12: 538. (1904).
Other accepted species: Species Fungorum – search Pichiomycetes.
Figure 1 – Microscopic features of taxa in Saccharomycotina. a Septate non-sporulating hyphae and pseudohyphae of Alloascoidea hylecoeti (Alloascoideaceae, Alloascoideales, Alloascoideomycetes). b-d Alloascoidea africana (Alloascoideaceae, Alloascoideales, Alloascoideomycetes) asci with ascospores and released ascospores (indicated with arrows). e,f Dipodascus albidus (Dipodascaceae, Dipodascales, Dipodascomycetes). e. Ascospores within hyphae and released ascospores. f Hyphae, arthroconidia and ascospores (indicated by arrow). g Lipomyces starkeyi (Lipomycetaceae, Lipomycetales, Lipomycetes) conjugation between a cell and its bud, ascus with ellipsoidal ascospores (indicated by arrows). h-j Pichia membranifaciens (Pichiaceae, Pichiales, Pichiomycetes) budding cells and asci with hat-shaped ascospores (indicated by arrows). k Pachysolen tannophilus (Pachysolenaceae, Alaninales, Pichiomycetes) budding cells, ascus with ascospores and liberated ascospores (indicated by arrow). l,m Metschnikowia bicuspidata (Metschnikowiaceae, Serinales, Pichiomycetes). (l) M. bucuspidata var. californica budding cells and needle-shaped ascospores. (m) M. bucuspidata var. chathamia budding cells and needle-shaped ascospores. n Saccharomyces cerevisiae (Saccharomycetaceae, Saccharomycetales, Saccharomycetes) budding cells and unconjugated, persistent ascus with globose ascospores (indicated by arrow). o, p Phaffomyces opuntiae (Phaffomycetaceae, Phaffomycetales, Saccharomycetes). (o) Budding cells and asci with hat-shaped ascospores (indicated by arrows). (p) Budding cells in short chains and asci with hat-shaped ascospores (indicated by arrows). q Saccharomycodes ludwigii (Saccharomycodaceae, Saccharomycodales, Saccharomycetes) bipolar cell division of budding cells and asci with spherical ascospores (indicated by arrows). r-t Ascoidea rubescens (Ascoideaceae, Ascoideales, Saccharomycetes). (r) Asexual cells and cluster of ascospores (indicated by arrow) (s) Asexual cells and septate hyphae, (t) Ascus with spores in different states of nascendi. u Sporopachydermia lactativora (Sporopachydermiaceae, Sporopachydermiales, Sporopachydermiomycetes) budding cells. v Trigonopsis variabilis (Trigonopsidaceae, Trigonopsidales, Trigonopsidomycetes). Budding cells with ellipsoidal and triangular morphology. Triangular cells produce ellipsoidal and triangular buds. Scale bar: a = 5μm, b-q, u,v = 10μm, r-t =30μm.
References
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 25 September 2026