The overwhelming majority of described fungal species are members of the subkingdom Dikarya (Hibbett et al. 2007), which is composed of the two phyla Ascomycota and Basidiomycota. Ascomycota is the largest phylum within the kingdom Fungi, with around 65,000 described species (Kirk et al. 2008).
Ascomycota, which includes both unicellular and multicellular forms, is divided into three monophyletic subphyla:
1) Taphrinomycotina (which includes, among others, Pneumocystis jirovecii, a fungus that is often present in the lungs of healthy people but can cause pneumocystosis in individuals with weakened immune systems);
2) Saccharomycotina (which includes the "true yeasts", including among others Saccharomyces cerevisiae [Bakers' Yeast] and Candida albicans, the most frequently encountered fungal pathogen of humans and often the agent responsible for vaginal yeast infections and thrush and some toenail infections, among others human medical woes);
Ascomycetes occur in terrestrial, marine, and freshwater habitats and many species play a major ecological role as decomposers. They range from microscopic to the size of large "mushrooms". The key characteristic of the Ascomycetes is the production of ascospores (by meiosis, usually followed by mitosis) in sac-like asci (singular: ascus) as part of their sexual reproduction (ascomycetes also reproduce asexually via the production of conidia, which are formed by mitosis at the tips of haploid conidiophores). In many ascomycete clades, these asci are enclosed in "fruiting bodies" (ascocarps), which include some very familiar forms such as truffles and morels.
In the vast majority of the symbiotic associations known as lichens, the fungal partner is an ascomycete (and a large fraction of ascomycete species are known from lichens). Many mycorrhizae (mutualistic associations between fungi and plant root systems) involve ascomycetes as well. A number of agriculturally important plant pathogens are ascomycetes--but so are the fungi that gave us penicillin and many cheeses (Ropars et al. 2012) and several ascomycete species have been major model organisms for research in genetics and cell biology.
(James et al. 2006; Hibbett et al. 2007; Kirk et al. 2008)
There are over 64,000 species of sac fungi. These fungi are named for the microscopic sacs their spores form in. Most lichens have a fungus from this family. A lichen is an organism formed by the symbiotic relationship of a fungus with an algae.
colony of Filobasidiella depauperata parasitises colony of anamorph of Ascomycetes
Remarks: Other: uncertain
Fungus / saprobe
apothecium of Rutstroemia juniperi is saprobic on old stroma of Ascomycetes
Remarks: season: 5-9
Evolution and Systematics
Free-living ascomycetes growing in colonies can spread into the extremely hostile environments including deserts because they possess extracellular polymeric substances and other adaptations.
“Rock-inhabiting MCF [microcolonial fungi] endure sudden changes in the environment by rapidly adapting their metabolic activity, life style and survival structures to the new conditions. Ultrastructural peculiarities of these fungi suggest spore-like metabolism and protection (Fig. 6) although MCF do not propagate sexually (Gorbushina, 2003; Gorbushina et al., 2003). Relevant characteristics of poikilo-tolerant MCF include: (i) the capacity to survive long periods of suspended metabolism. In this way, they can remain as colonies made up of pseudo tissue-like microcolonies comprising 100–500 cells for several decades until conditions favourable to further growth return; (ii) the ability to re-organize internally by constantly replacing dying or dead cells with new buds (Gorbushina et al., 2003) and Fig. 6C; (iii) the ability to form filamentous hyphae that develop from clump-like colonies (Fig. 5E) to penetrate deep into rocks thus protecting themselves from environmental stresses. In this sense, the visible portion of melanized MCF is like the tip-of-the-iceberg, because the hyphae can rapidly penetrate several mm to cm into hard rocks in search of more protected environments and; (iv) the ability to create a multitude of varnish-like coatings, skins and shells that arise from the impregnation of the extracellular matrix and melanin layers with minerals (Dragovich, 1984; 1993; 1998; Gorbushina, 2003).” (Gorbushina 2007:1619-1620)
Learn more about this functional adaptation.
Free-living ascomycetes survive unfavorable conditions by forming pseudo tissue-like microcolonies.
"The capacity to survive long periods of suspended metabolism allows free-living ascomycetes to remain as colonies made up of pseudo tissue-like microcolonies comprising 100–500 cells for several decades until conditions favourable to further growth return." (Gorbushina 2007:1620)
Learn more about this functional adaptation.
Molecular Biology and Genetics
Statistics of barcoding coverage
Specimens with Sequences:68994
Specimens with Barcodes:57868
Species With Barcodes:16054
To request an improvement, please leave a comment on the page. Thank you!