Ascomycota
Ascomycota is a phylum of fungi characterized by the production of sexual spores within a sac-like structure called an ascus. This diverse group includes many important plant pathogens, as well as edible fungi like morels and truffles. Ascomycota play crucial roles in ecosystems as decomposers, symbionts, and pathogens, and have significant economic and ecological impacts.
7 Key excerpts on "Ascomycota"
eBook - ePub- J. W. Deacon(Author)
- 2013(Publication Date)
- Wiley-Blackwell(Publisher)
...A single ascospore can give rise a colony that will produce the sexual stage. Ecology and significance Because the Ascomycota is a very large and important phylum, many aspects of its biology are covered in the later chapters of this book. The group as a whole includes many economically important plant pathogens, such as the powdery mildew fungi of many crop plants (Chapter 14), the vascular wilt fungi (Chapter 14), Ophiostoma ulmi and O. novo-ulmi, which cause the devastating Dutch elm disease that swept repeatedly across Europe and the USA in the last century (Chapter 10), the equally devastating chestnut blight disease in the USA, caused by Cryphonectria parasitica (Chapter 9) and several toxigenic fungi, such as Claviceps purpurea (ergot of cereals; Chapter 7). The Ascomycota also includes several pathogens of humans, domesticated animals and livestock. For example, the ubiquitous dermatophytic (ringworm) fungi are estimated to infect about half of the total human population, especially in the tropics and subtropics, but also in developed countries, where infections such as “athlete’s foot” and “nail fungus” are common. The ascomycetous yeast, Candida albicans, is a common commensal organism in the gut and on other mucosal membranes of humans, causing irritation to people who wear dentures and to women during menstruation or pregnancy. And, some ascomycetous fungi (Blastomyces dermatitidis, Histoplasma capsulatum) can cause life-threatening diseases of humans whose immune system is deficient or impaired. The “Moulds of Man” are covered in Chapter 16. In a different context, some of the Ascomycota form mycorrhizal associations with forest trees (e.g. Tuber spp – the truffles) and an estimated 96% of the 13,500 known species of lichens have Ascomycota as the fungal partner. Very few of these lichenized fungi grow in a free-living state...
eBook - ePub- Sarah C. Watkinson, Lynne Boddy, Nicholas Money(Authors)
- 2015(Publication Date)
- Academic Press(Publisher)
...The phylum includes yeasts and filamentous fungi, fungi that partner with algae and cyanobacteria to form lichen symbioses, mycorrhizal species, saprotrophs, and pathogens of plants and animals. Ascomycetes are utilised in industrial applications, in food production and flavouring, and the fruit bodies of morels and truffles are prized edible fungi. Many species are known only as asexual fungi (anamorphs) that produce asexual spores (conidia) on stalks called conidiophores (Figure 1.12), but sexual phases (teleomorphs) have been identified in the life cycles of most ascomycetes that have been studied in detail. The sexual organs formed by ascomycetes are called ascomata (s. ascoma, Figure 1.13). Ascomata include open cup-shaped fruit bodies (apothecia), flask-shaped structures with a single vent for spore release (perithecia), and fruit bodies that develop as closed structures that open in a variety of ways to release spores (cleistothecia). Ascomata contain the characteristic spore-producing cells of the phylum called asci (s. ascus). The sexual spores of ascomycetes, called ascospores, form inside asci. This internal development of ascospores contrasts with the production of basidiospores on the outside of basidia in the Basidiomycota (compare Figure 1.14 with Figure 1.7). The hyphae of ascomycetes lack the dolipore septa and clamp connections of basidiomycetes; their septa have a single, central pore. Mobile organelles (microbodies) with dense protein cores, called Woronin bodies, plug the septal pores and isolate damaged hyphal compartments from the rest of the colony. These organelles are found in the largest subphylum, the Pezizomycotina, which contains 90% of the Ascomycota, but are absent from the other members of the phylum (whose groups are detailed below). Figure 1.12 Selection of conidial stages, or anamorphs, of ascomycetes. (a) Basipetospora variabilis, a soil fungus...
eBook - ePubWood Microbiology
Decay and Its Prevention
- Robert A. Zabel, Jeffrey J. Morrell(Authors)
- 2020(Publication Date)
- Academic Press(Publisher)
...These fungi are characterized by rapid growth and abundant production of spores. Their role in wood is not clear, but they cause little or no damage beyond cosmetic effects on the wood surface. The Ascomycotina and basidiomycotina are by far the most prevalent fungi in wood and play important roles in carbon recycling. There has been a revolution in fungal classification which has shifted from a morphological system based primarily on fruiting bodies to one that includes more detailed information on genetic composition. For example, one of the most important morphological attributes for separating the Ascomycota was whether the ascus was unitunicate or bitunicate. However, this morphological separation has been replaced by a taxonomy based upon DNA sequences. The group is currently divided into three Sub-phylla: Pezizomycotina, Saccharomycotina, and Taphrinamycota. The Pezziomycotina includes all of the species that produce an ascocarp and includes some wood decay fungi. The Saccharomycotina includes single celled species such as yeasts that reproduce by vegetative budding (Saccharomyces spp., an industrial yeast and Endomycopsis fasiculata - a yeast growing in ambrosia beetle tunnels), while the Taphrinomycotina are a mixture species including some plant pathogens...
eBook - ePubHandbook of Microbiology
Condensed Edition
- Allen I Laskin(Author)
- 2019(Publication Date)
- CRC Press(Publisher)
...Sermonti 81 discusses the genetics of industrial microbiology. The Ascocarp Ascogenous hyphae are contained within the ascocarp in all Ascomycetes except the Hemiascomycetes. In the Euascomycetes the body is in the form of a cleistothecium, perithecium, or apothecium (Figure 5) and is believed by some to be developed in response to sexual stimulation during formation of the ascogenous hyphae. In the Loculoascomycetes the stroma forms before the ascogonium (Figure 5) develops and, therefore, probably is not developed in response to a sexual stimulus (see References 16 and 185 for discussions of possible stimulation). The ascocarp, with or without stroma, is composed of pseudoparenchymatous or prosenchymatous tissue (Figure 7). Ascospores are either ejected forcibly from the ascocarp if the asci remain intact, or issue from the ascocarp as a fluid mass if the asci dissolve while inside the ascocarp. Ecology Terrestrial Ascomycetes Terrestrial Ascomycetes, for the most part, live on dung (coprophilous), wood (lignicolous), grass (graminicolous), insects (insecticolous), rocks (saxicolous; for example, in lichen associations), leaves and stems (foliicolous and caulicolous), on the ground (terricolous), on bark (corticolous), in the soil, in and on roots (mycorrhizal, saprophytic, and parasitic), and in and on animals other than insects. Since there are 1,950 genera and 15,000 species of Ascomycetes, only a cursory consideration of them and their activities can be presented. Soil Fungi Soil is an heterogeneous material, consisting mainly of inorganic colloids and associated ions, salts, sand, pebbles, gas, and humus and other organic matter. Soil is the temporary site of dead animal bodies, plant debris, and living and dead plant roots. Microorganisms observed to be growing on these need not necessarily be soil microbes...
eBook - ePub- (Author)
- 2019(Publication Date)
- Wiley-Blackwell(Publisher)
...For a given pleomorphic species, mycologists used to give the anamorph (e.g., Aspergillus fumigatus) a distinct name from their teleomorph form (e.g., Neosartorya fumigata). According to the newly adopted International Code of Nomenclature for algae, fungi, and plants (ICN), dimorphic fungi now bear a single name (“one fungus, one name policy”) instead of the previous dual nomenclature (78). In the genus Aspergillus, many species are able to reproduce sexually but for many of them the sexual state is still unknown (previously classified as fungi imperfecti or Deuteromycetes). The production of meiotic ascospores by teleomorphs and cumulative molecular phylogenetic analyses have led some taxonomists to suggest that all Aspergillus species, including anamorphs, could be placed within the phylum Ascomycota (9, 24). Mycotic diseases are relatively uncommon but are often devastating to the infected host. Most fungi are decomposers subsisting primarily on plant materials and other organic debris but can attack living hosts under certain conditions. Most clinically important fungi, other than yeasts, produce large amounts of airborne spores for dissemination. Except for the dermatophytoses, which affect the integument, animals are dead‐end hosts for fungal infections, because they are not contagious (44). Histoplasmosis and cryptococcosis are rare fungal infections of poultry but are notable as public health hazards. Information on these can be found in previous editions of this book (44). This chapter does not address mycotoxicosis (see Chapter 31) following ingestion of secondary metabolites of fungal origin. Aspergillosis Introduction Definition and Synonyms Invasive and noninvasive infections of vertebrates caused by opportunistic pathogens of the genus Aspergillus are collectively named aspergillosis (93). Manifestations of the disease depend on which organs or systems are involved and whether the infection is localized or disseminated...
...Whatever the reason, they lag immeasurably behind Ascomycetes in the formation of lichens. b. Ascolichens. Lichens are again polyphyletic within this sub-class. The main groups from which they are derived are evident. Whether there has been a series of origins within the different groups or a development from one starting point in each it would be difficult to determine. In any case great changes have taken place after symbiosis became established. The main divisions within the Ascolichens are related to fungi thus: Series 1. Pyrenocarpineae } to Pyrenomycetes. 2. Coniocarpineae } 3. Graphidineae to Hysteriaceae. 4. Cyclocarpineae to Discomycetes. II. THE REPRODUCTIVE ORGANS A. Theories of Descent in Ascolichens It has been suggested that ascomycetous fungi, from which Ascolichens are directly derived, are allied to the Florideae, owing to the appearance of a trichogyne in the carpogonium of both groups. That organ in the red seaweeds is a long delicate cell in direct communication with the egg-cell of the carpogonium. It is a structure adapted to totally submerged conditions, and fitted to attach the floating spermatia. In fungi there is also a structure considered as a trichogyne [981], which, in the Laboulbeniales, is a free, simple or branching organ. There is no other instance of any similar emergent cell or cells connected with the ascogonium of the Ascomycetes, though the term has been applied in these fungi to certain short hyphal branches from the ascogonium which remain embedded in the tissue. In the Ascomycetes examined all traces of emergent receptive organs, if they ever existed, have now disappeared; in some few there are possible internal survivals which never reach the surface. In Ascolichens, on the contrary, the “trichogyne,” a septate hyphal branch extending upwards from the ascogonium, and generally reaching the open, has been demonstrated in all the different groups except, as yet, in the Coniocarpineae which have not been investigated...
eBook - ePub- Colin K. Campbell, Elizabeth M. Johnson, David W. Warnock, David W. Warnock(Authors)
- 2013(Publication Date)
- Wiley-Blackwell(Publisher)
...APPENDIX 1 COMMON MYCOLOGICAL TERMS acervulus (pl. acervuli) : an open or cup-shaped structure on which conidia are formed. acropetal: a chain of conidia in which new conidia are formed at the tip of the chain. aleuriospore: a thallic conidium that is formed from the end of an undifferentiated hypha, or from a short side-branch. anamorph: the asexual form of a fungus. annellide: a specialized conidiogenous cell from which enteroblastic spores are produced and which has a column of apical scars (annellations) at its tip. apophysis: the enlargement of a sporangiophore below the columella. arthrospore: a thallic conidium produced as a result of fragmentation of an existing hypha into separate cells. ascocarp: a structure that contains asci. ascoma (pl. ascomata) : see ascocarp. ascospore: a haploid spore produced within an ascus following meiosis. ascus (pl. asci) : a thin-walled sac containing ascospores, characteristic of the Ascomycota. aseptate: without cross-walls or septa. asteroid body: radiating material surrounding fungal cells in chronic infection. ballistospore: a conidium or other spore that is forcibly discharged. basidiocarp: a structure that produces basidia. basidioma (pl. basidiomata) : see basidiocarp. basidiospore: a haploid spore produced on a basidium following meiosis. basidium (pl...
