Ascomycota is another name for tubular fungi, which come in very different forms. They are found in almost all habitats and their range moves from being very useful (for making food such as bread, beer, wine, etc.) to being valuable and tasty edible fungi (such as truffles and morels) to causing serious infectious diseases, such as those caused by Candida or Aspergillus species.
What are ascomycota?
Ascomycota (tubular fungi) form one of the large divisions of fungi, with more than 20,000 species. They owe their name to their tubular reproductive organs, the asci, in which the reduction division of the haploid ascospores takes place in the case of sexual reproduction. Characteristic of most Ascomycota are their cell filaments, which measure an average of five micrometers and are called hyphae. They are usually multicellular, branch many times and together form a meshwork, the mycelium. The individual cells of the hyphae have cell walls that are mostly composed of chitin and beta-glucans. Even within a hypha, the individual cells are separated by cell walls, so that if a hypha is injured, only the cytoplasm of this one cell can escape, and the rest of the hypha, including its cytoplasm, remains intact. However, there are also unicellular Ascomycota that do not form hyphae, as in some yeasts. In the course of sexual reproduction, some tubular fungi produce underground or above-ground fruiting bodies, some of which are highly desirable and very expensive as edible mushrooms. These include truffles and some morel species. Molds (Aspergillus) also belong to the Ascomycota. Many Ascomycota have the ability to capture algae or cyanobacteria capable of photosynthesis and form a symbiotic relationship with them. These are so-called lichens, which were probably the first land dwellers on earth to create the conditions for the development of plants and animals by decomposing rocks and using photosynthesis. Another importance has tubular fungi species, which with their hyphae can form a symbiotic relationship, called mycorrhiza, with the hair roots of trees and almost all other plants.
Occurrence, distribution and characteristics
Ascomycota are found in almost all land-based habitats. Except for yeast cells, tubular fungal species are mostly haploid, that is, have only a single set of chromosomes. Reproduction is largely by asexual sporulation, which develops in specialized cells called conidia. Some species also have sexual development with the formation of ascospores in tube-like structures called asci. Ascomycota mostly occur as saprophytes, recyclers and decomposers of residual biomass. Some species may also be called “carnivorous” because their hyphae can capture, kill, and digest, for example, amoebae, rotifers, tardigrades, nematodes, and other organisms. Some species that are normally ubiquitous in the soil also appear as kerosene or diesel fungi. They can spread in aircraft fuel tanks or diesel vehicle tanks and cause blockages or other damage to fuel lines. Various physiological properties of certain species of tubular fungi are used, for example, to obtain antibiotics or for the gentlest possible immunosuppression to suppress rejection reactions. The pathogenic properties of some Ascomycota, which can lead to pneumonia and fungal infections of the skin, usually indicate a weakened or artificially suppressed immune system. There is no risk of human-to-human infection. More dangerous may be the effects of inhaled highly toxic substances produced by plant-infecting tube fungi, such as ergot fungus.
Significance and function
Ascomycota have a very high – mostly indirect – importance for health, which far outweighs their pathogenic potential in principle. Immediate beneficial effects consist in the fact that penicillin is obtained from tubular fungal cultures (mold), which, as an antibiotic, has revolutionized the treatment of bacterial infections for many decades.Ciclosporin, which is also produced by tube fungi, is a very effective agent used for immunosuppression after organ transplants and may also play a role in the future in suppressing autoimmune reactions in diseases such as Hashimoto’s or multiple sclerosis (MS). In addition, various enzymes such as insulin or agents for dissolving thrombi and other substances with specific health relevance can be produced from genetically modified tubular fungi. Various species of sac fungi are of indirect relevance to health in the production of foodstuffs. These are mainly baker’s yeasts, fermentation yeasts for the production of wine and beer, and molds for the production of well-known cheeses such as Roquefort and Gorgonzola. Direct influence on human metabolism is also exerted by the few tubular mushroom species that are not only well suited for consumption as edible and gourmet mushrooms, but also provide important minerals, amino acids, glucans and polysaccharides. These are mushroom varieties such as truffle and morel.
Diseases and ailments
Similar to health effects, Ascomycota can pose immediate and indirect hazards. Immediate hazards take the form of infection with tubular fungi such as Candida or Aspergillus species. In the case of a weakened immune system, the fungus, which belongs to the unicellular yeast fungi, can cause infections on the skin and mucous membranes, a candidosis. Likewise, some types of molds can cause infections, so-called aspergilloses. The lungs are frequently affected. Allergies to the spores of Aspergillus molds are also widespread. Some Ascomycota release highly toxic toxins, some of which are also used in pharmaceuticals. For example, ergot alkaloids synthesized by molds find use in the pharmaceutical industry for the production of specific active ingredients. The pharmacological effects of ergot alkaloids are very diverse. They have stimulatory or inhibitory effects on some hormone receptors. For example, ergot alkaloids can inhibit the secretion of prolactin and somatotropin.
