Fungus

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"Fungi" redirects here. For other uses, see Fungi (disambiguation).

Fungi

Temporal range:

Early Devonian – Present (but see

text) 410–0 Ma 

PreꞒ

Pg

N
 Clockwise from top left:

 Amanita muscaria, a basidiomycete;

Sarcoscypha coccinea, an ascomycete;

 bread covered in mold;

 a chytrid;

 an Aspergillus conidiophore.

Scientific classification

(unranked): Opisthokonta

(unranked): Holomycota

(unranked): Zoosporia

Kingdom: Fungi
(L.) R.T.Moore[1]

Subkingdoms/Phyla

 Rozellomyceta
o Rozellomycota
o Microsporidia
 Aphelidiomyceta
o Aphelidiomycota
 Eumycota
o Chytridiomyceta
 Neocallimastigomyc
ota
 Chytridiomycota
o Blastocladiomyceta
 Blastocladiomycota
o Zoopagomyceta
 Basidiobolomycota
 Entomophthoromyc
ota
 Kickxellomycota
o Mortierellomycota
o Mucoromyceta
 Calcarisporiellomyc
ota
  Mucoromycota
o Symbiomycota
 Glomeromycota
 Entorrhizomycota
 Dikarya
 Basidiomycota
 Ascomycota

A fungus (plural: fungi[2] or funguses[3]) 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 a kingdom,
separately from the other eukaryotic kingdoms, which by one traditional classification
include Plantae, Animalia, 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), which share a common
ancestor (from 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 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.
 The fungus kingdom encompasses an enormous diversity of taxa with varied
ecologies, life cycle strategies, and morphologies ranging from unicellular
aquatic chytrids to large mushrooms. However, little is known of the
true biodiversity of Kingdom Fungi, which has been estimated at 2.2 million to
3.8 million species.[4] Of these, only about 148,000 have been described, [5] with over
8,000 species known to be detrimental to plants and at least 300 that can be
pathogenic to humans.[6] Ever since the pioneering 18th and 19th
century taxonomical works of Carl Linnaeus, Christiaan Hendrik Persoon, and Elias
Magnus Fries, fungi have been classified according to their morphology (e.g.,
characteristics such as spore color or microscopic features) or physiology. Advances
in molecular genetics have opened the way for DNA analysis to be incorporated into
taxonomy, which has sometimes challenged the historical groupings based on
morphology and other traits. Phylogenetic studies published in the first decade of the
21st century have helped reshape the classification within Kingdom Fungi, which is
divided into one subkingdom, seven phyla, and ten subphyla.

Contents

 1Etymology
 2Characteristics
 3Diversity
 4Mycology
o 4.1History
 5Morphology
o 5.1Microscopic structures
o 5.2Macroscopic structures
 6Growth and physiology
 7Reproduction
o 7.1Asexual reproduction
o 7.2Sexual reproduction
o 7.3Spore dispersal
o 7.4Homothallism
o 7.5Other sexual processes
 8Evolution
 9Taxonomy
o 9.1Taxonomic groups
o 9.2Fungus-like organisms
 10Ecology
o 10.1Symbiosis
 10.1.1With plants
 10.1.2With algae and cyanobacteria
 10.1.3With insects
 10.1.4As pathogens and parasites
 10.1.5As targets of mycoparasites
 11Mycotoxins
 12Pathogenic mechanisms
 13Human use
o 13.1Therapeutic uses
 13.1.1Modern chemotherapeutics
o 13.2Traditional medicine
 o 13.3Cultured foods
o 13.4In food
o 13.5Poisonous fungi
o 13.6Pest control
o 13.7Bioremediation
o 13.8Model organisms
o 13.9Others
 14See also
 15References
o 15.1Cited literature
 16External links

Etymology
The English word fungus is directly adopted from the Latin fungus (mushroom), used
in the writings of Horace and Pliny.[7] This in turn is derived from
the Greek word sphongos (σφόγγος 'sponge'), which refers to
the macroscopic structures and morphology of mushrooms and molds;[8] the root is
also used in other languages, such as the German Schwamm ('sponge')
and Schimmel ('mold').[9]
The word mycology is derived from the Greek mykes (μύκης 'mushroom')
and logos (λόγος 'discourse').[10] It denotes the scientific study of fungi. The Latin
adjectival form of "mycology" (mycologicæ) appeared as early as 1796 in a book on
the subject by Christiaan Hendrik Persoon.[11] The word appeared in English as early
as 1824 in a book by Robert Kaye Greville.[12] In 1836 the English naturalist Miles
Joseph Berkeley's publication The English Flora of Sir James Edward Smith, Vol.
5. also refers to mycology as the study of fungi.[8][13]
A group of all the fungi present in a particular region is known as mycobiota (plural
noun, no singular).[14] The term mycota is often used for this purpose, but many
authors use it as a synonym of Fungi. The word funga has been proposed as a less
ambiguous, parallel term equivalent to fauna and flora.[15]

Characteristics

Fungal hyphae cells

1. Hyphal wall
2. Septum
3. Mitochondrion
4. Vacuole
5. Ergosterol crystal
6. Ribosome
7. Nucleus
8. Endoplasmic reticulum
9. Lipid body
10. Plasma membrane
11. Spitzenkörper
12. Golgi apparatus

Fungal cell cycle showing Dikaryons typical of Higher Fungi

Before the introduction of molecular methods for phylogenetic

analysis, taxonomists considered fungi to be members of the plant kingdom because
of similarities in lifestyle: both fungi and plants are mainly immobile, and have
similarities in general morphology and growth habitat. Like plants, fungi often grow in
soil and, in the case of mushrooms, form conspicuous fruit bodies, which sometimes
resemble plants such as mosses. The fungi are now considered a separate kingdom,
distinct from both plants and animals, from which they appear to
have diverged around one billion years ago (around the start of
the Neoproterozoic Era).[16][17] Some morphological, biochemical, and genetic features
are shared with other organisms, while others are unique to the fungi, clearly
separating them from the other kingdoms:
Shared features:

 With other eukaryotes: Fungal cells contain membrane-

bound nuclei with chromosomes that contain DNA with noncoding
regions called introns and coding regions called exons. Fungi have membrane-
bound cytoplasmic organelles such as mitochondria, sterol-containing
membranes, and ribosomes of the 80S type.[18] They have a characteristic range
of soluble carbohydrates and storage compounds, including sugar
alcohols (e.g., mannitol), disaccharides, (e.g., trehalose),
and polysaccharides (e.g., glycogen, which is also found in animals[19]).
 With animals: Fungi lack chloroplasts and are heterotrophic organisms and so
require preformed organic compounds as energy sources.[20]
 With plants: Fungi have a cell wall[21] and vacuoles.[22] They reproduce by both
sexual and asexual means, and like basal plant groups (such
as ferns and mosses) produce spores. Similar to mosses and algae, fungi
typically have haploid nuclei.[23]
 With euglenoids and bacteria: Higher fungi, euglenoids, and some bacteria
produce the amino acid L-lysine in specific biosynthesis steps, called the α-
aminoadipate pathway.[24][25]
 The cells of most fungi grow as tubular, elongated, and thread-like (filamentous)
structures called hyphae, which may contain multiple nuclei and extend by
growing at their tips. Each tip contains a set of aggregated vesicles—cellular
 structures consisting of proteins, lipids, and other organic molecules—called
the Spitzenkörper.[26] Both fungi and oomycetes grow as filamentous hyphal cells.
[27]
 In contrast, similar-looking organisms, such as filamentous green algae, grow
by repeated cell division within a chain of cells. [19] There are also single-celled
fungi (yeasts) that do not form hyphae, and some fungi have both hyphal and
yeast forms.[28]
 In common with some plant and animal species, more than 70 fungal
species display bioluminescence.[29]
Unique features:

 Some species grow as unicellular yeasts that reproduce

by budding or fission. Dimorphic fungi can switch between a yeast phase and a
hyphal phase in response to environmental conditions. [28]
 The fungal cell wall is made of glucans and chitin; while glucans are also found in
plants and chitin in the exoskeleton of arthropods,[30] fungi are the only organisms
that combine these two structural molecules in their cell wall. Unlike those of
plants and oomycetes, fungal cell walls do not contain cellulose. [31][32]

Omphalotus nidiformis, a bioluminescent mushroom

Most fungi lack an efficient system for the long-distance transport of water and
nutrients, such as the xylem and phloem in many plants. To overcome this limitation,
some fungi, such as Armillaria, form rhizomorphs,[33] which resemble and perform
functions similar to the roots of plants. As eukaryotes, fungi possess a biosynthetic
pathway for producing terpenes that uses mevalonic
acid and pyrophosphate as chemical building blocks.[34] Plants and some other
organisms have an additional terpene biosynthesis pathway in their chloroplasts, a
structure that fungi and animals do not have. [35] Fungi produce several secondary
metabolites that are similar or identical in structure to those made by plants. [34] Many
of the plant and fungal enzymes that make these compounds differ from each other
in sequence and other characteristics, which indicates separate origins
and convergent evolution of these enzymes in the fungi and plants. [34][36]

Diversity
Bracket fungi on a tree stump

Fungi have a worldwide distribution, and grow in a wide range of habitats, including
extreme environments such as deserts or areas with high salt
concentrations[37] or ionizing radiation,[38] as well as in deep sea sediments.[39] Some
can survive the intense UV and cosmic radiation encountered during space travel.
[40]
 Most grow in terrestrial environments, though several species live partly or solely
in aquatic habitats, such as the chytrid fungi Batrachochytrium
dendrobatidis and B.  salamandrivorans, parasites that have been responsible for a
worldwide decline in amphibian populations. These organisms spend part of their life
cycle as a motile zoospore, enabling them to propel itself through water and enter
their amphibian host.[41] Other examples of aquatic fungi include those living
in hydrothermal areas of the ocean.[42]
As of 2020, around 148,000 species of fungi have been described by taxonomists,
[5]
 but the global biodiversity of the fungus kingdom is not fully understood. [43] A 2017
estimate suggests there may be between 2.2 and 3.8 million species.[4] The number
of new fungi species discovered yearly has increased from 1,000 to 1,500 per year
about 10 years ago, to about 2000 with a peak of more than 2,500 species in 2016.
In the year 2019, 1882 new species of fungi were described, and it was estimated
that more than 90% of fungi remain unknown.[5] In mycology, species have historically
been distinguished by a variety of methods and concepts. Classification based
on morphological characteristics, such as the size and shape of spores or fruiting
structures, has traditionally dominated fungal taxonomy. [44] Species may also be
distinguished by their biochemical and physiological characteristics, such as their
ability to metabolize certain biochemicals, or their reaction to chemical tests.
The biological species concept discriminates species based on their ability to mate.
The application of molecular tools, such as DNA sequencing and phylogenetic
analysis, to study diversity has greatly enhanced the resolution and added
robustness to estimates of genetic diversity within various taxonomic groups.[45]