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Some species of Ascomycete may not always
have a functional spore-bearing ascus. Those belonging
to the group previously known as Deuteromycota, also
known as Fungi Imperfectii, are asexual in nature and
therefore have no need for a sac to hold spores. However,
they may possess at least a morphological or physiological
analog of the ascus. Such species, for example Penicilium
from where the medicine penicillin is derived, are recognized
as Ascomycetes. The phrase "ascomycetous fungi"
is also used to describe these kinds of organisms.
Ascomycetes are the largest group of fungi.
There are well over 60,000 species identified and they
are found widespread all over the world. In every continent,
from Asia, Europe, North and South America, Australia,
Africa and even in Antarctica, Ascomycetes abound. Some
species are known to be able to develop adaptations
and symbiotic relationships with various plants and
animals (as in lichens) for survival in extreme environments.
Ascomycete spores are ever-present in the atmosphere.
While some Ascomycete species can be found
just about everywhere, there are others that are extremely
localized. For example, Tuber magnatum (more popularly
known as white truffle) is endemic only to specific
areas of France and Italy. These species of habitat-limited
fungi are mostly Ascomycetes that are, in most likelihood,
symbionts with particular plant or animal life.
Phylum Ascomycota is further classified
into 3 sub-phyla - Pezizomycotina, Saccharomycotina,
and Taphrinomycotina. Because of the vast diversity
of species under the Ascomycota group, they all come
in multi-varied colors, smells, growth rates, shapes
and sizes. Some Ascomycetes can be simple single-celled
organisms such as Saccharomyces cerevisiae, commonly
known as baker's yeast. The more complex multi-cellular
Ascomycetes include Erysiphales (powdery mildew), Morchella
(morels), Tuber (truffles), Cladonia (moss-like lichens),
and Penicillium (penicillin).
Several Ascomycetes are known pathogens
to both plants and animals, including humans. Some of
the plant diseases produced by Ascomycetes are Dutch
elm disease, chestnut blight, powdery mildew, and ergot.
The latter also affects humans by long-term ergot poisoning
called ergotism. Other human diseases caused by Ascomycete
species include candidiasis from Candida albicans, various
dermatomycoses or skin infections from Epidermophyton,
and pulmonary infections which may be severe and life-threatening
for patients with impaired immune systems.
Despite the threats posed by various Ascomycetes,
they serve a pivotal role in the ecology. They help
in the decomposition of dead organic materials and are
a source of food for insects, gastropods and even small
to mid-sized mammals like a variety of rodents, pigs
and deer.
Ascomycetes are also sources for food
and medicine for humans. A notable example is Penicillin,
which is derived from Penicillium chrysogenum. Other
Ascomycetes are used for the production of insulin and
HGH (human growth hormone) for therapeutic purposes.
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