A
fungus (
pl.:
fungi or
funguses) is any member of the group of
eukaryotic organisms that includes microorganisms such as
yeasts and
molds, as well as the more familiar
mushrooms. These organisms are classified as one of the
traditional eukaryotic kingdoms, along with
Animalia,
Plantae and either
Protista or
Protozoa and
Chromista.
A characteristic that places fungi in a different kingdom from
plants,
bacteria, and some
protists is
chitin in their
cell walls. Fungi, like animals, are
heterotrophs; they acquire their food by absorbing dissolved molecules, typically by secreting
digestive enzymes into their environment. Fungi do not
photosynthesize. Growth is their means of
mobility, except for
spores (a few of which are
flagellated), which may travel through the air or water. Fungi are the principal
decomposers in ecological systems. These and other differences place fungi in a single group of related organisms, named the
Eumycota (
true fungi or
Eumycetes), that share a
common ancestor (i.e. they form a
monophyletic group), an interpretation that is also strongly supported by
molecular phylogenetics. This fungal group is distinct from the structurally similar
myxomycetes (slime molds) and
oomycetes (water molds). The discipline of
biology devoted to the study of fungi is known as
mycology (from the
Greek μύκης mykes, mushroom). In the past mycology was regarded as a branch of
botany, although it is now known that fungi are genetically more closely related to animals than to plants.
Abundant worldwide, most fungi are inconspicuous because of the small size of their structures, and their
cryptic lifestyles in soil or on dead matter. Fungi include
symbionts of plants, animals, or other fungi and also
parasites. They may become noticeable when
fruiting, either as mushrooms or as molds. Fungi perform an essential role in the decomposition of organic matter and have fundamental roles in nutrient
cycling and exchange in the environment. They have long been used as a direct
source of human food, in the form of mushrooms and
truffles; as a
leavening agent for bread; and in the
fermentation of various food products, such as
wine,
beer, and
soy sauce. Since the 1940s, fungi have been used for the production of
antibiotics, and, more recently, various
enzymes produced by fungi are used
industrially and in
detergents. Fungi are also used as
biological pesticides to control weeds, plant diseases, and insect pests. Many species produce
bioactive compounds called
mycotoxins, such as
alkaloids and
polyketides, that are toxic to animals, including humans. The fruiting structures of
a few species contain
psychotropic compounds and are consumed
recreationally or in traditional
spiritual ceremonies. Fungi can break down manufactured materials and buildings, and become significant
pathogens of humans and other animals. Losses of crops due to fungal diseases (e.g.,
rice blast disease) or
food spoilage can have a large impact on human
food supplies and local economies. (
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