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a phylum of the kingdom FungiFungi
, kingdom of heterotrophic single-celled, multinucleated, or multicellular organisms, including yeasts, molds, and mushrooms. The organisms live as parasites, symbionts, or saprobes (see saprophyte).
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A phylum in the kingdom Fungi, representing the largest of the major groups of fungi, and distinguished by the presence of the ascus, a specialized saclike cell in which fusion of nuclei and reduction division occur and the resulting nuclei form ascospores. In most ascomycetes, each ascus contains eight ascospores, but the number may vary from one to several hundred. In the simplest ascomycetes (yeasts), the vegetative body (thallus) is unicellular; however, in the majority of ascomycetes, the thallus is more complex and consists of a tubular, threadlike hypha with cross walls which grows in or on the substrate. These hyphae eventually form structures called ascomata (ascocarps), on or in which the asci are formed. In addition to their sexual reproduction, most ascomycetes reproduce asexually by means of conidia.

Traditionally, the structure of the ascoma and ascus has served as the basis for subdividing the Ascomycota into five classes: Hemiascomycetes, Plectomycetes, Pyrenomycetes, Discomycetes, Loculoascomycetes. The introduction of molecular data, however, is changing concepts of the relationships of different groups of ascomycetes and will eventually lead to a much-revised classification scheme.

The ascomycetes occur throughout the world in all types of habitats and on both living and dead substrates. An estimated 33,000 species are arranged in about 3300 genera, with new species being described regularly. Ecologically ascomycetes function as primary decomposers of plant materials, but they also are important as plant and human pathogens; in baking, brewing, and winemaking; in enzyme and acid production; and as sources of antibiotics and other drugs. See Eumycota, Fungi, Plant pathology, Yeast

McGraw-Hill Concise Encyclopedia of Bioscience. © 2002 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Kodamaea kakaduensis and Candida tolerates, two new ascomycetous yeast species from Australian Hibiscus flowers.
At least 134 species from 30 families of Basidiomycetous fungi and at least 19 species from 11 families of Ascomycetous fungi were positively identified during this study (Table 1).
Because the monoclonal antibodies were derived from a single lymphocyte, were screened for Neotyphodium specificity, and were selected against cross reaction to other ascomycetous fungi, it is likely that an immunological test based on monoclonal antibodies may reduce the incidence of false readings when screening samples.
Phylogenetic analysis identifies the megabacterium of birds as a novel anamorphic ascomycetous yeast, Macrorhabdus omithogaster gen.
Colonization of roots of cultivated Solanum lycopersicum by dark septate and other ascomycetous endophytes.
For this study 134 species from 30 families of Basidiomycetous fungi and 19 species from 11 families of Ascomycetous fungi were collected from different sites in Northeastern Ohio (Cuyahoga, Geauga, and Portage Counties).
Based on unique segments of genetic material, or DNA, the researchers had cataloged representative strains of all ascomycetous yeasts, a group so named because they reproduce sexually in saclike structures called asci.
These symbiotic associations that form mainly between woody angiosperms or gymnosperms and basidiomycetous or ascomycetous fungi (Malloch et al., 1980) can have root hair involvement.
During the course of our continuing search for new bioactive natural products from this kind of fungal species, an ascomycetous fungus Cytospora sp.
Many ascomycetous fungi naturally synthesize and secrete pigments and may thus provide a more reliable source for natural, "organic" food colourants with improved functionalities (3).