Fungi Design by Owen Borville October 30, 2024
Fungi are living organisms that have the characteristics of both plants and animals and their classification is complicated. Fungi do not perform photosynthesis and are heterotrophic, relying on organic compounds for energy. Fungi have few characteristics shared with other organisms and an evolutionist lineage is difficult to make for these organisms.
Fungi cell walls, a characteristic of plants, are composed of chitin, a characteristic of animals. Fungi produce animal-like pigments. Also like animals, fungi store carbohydrates as glycogen. Fungi act like bacteria when they absorb nutrients across their surface and behave like decomposers by recycling nutrients and breaking down organic materials.
Some fungi reproduce only asexually while some reproduce both asexually and sexually with alternation of generations. Most fungi produce large amounts of spores, haploid cells that undergo mitosis to form multicellular haploid individuals.
Most terrestrial plants develop symbiotic relationships with fungi, such as when the plant roots and underground fungi parts share nutrients (mycorrhizae). Lichens form a symbiotic association with fungus and algae.
Fungi also cause major infectious diseases in plants, animals, and humans. But fungi have commercial applications in the food industry with yeast and fermentation, enzymes and antibiotics. The scientific study of fungi is called mycology.
Fungi are eukaryotes and have a membrane-bound nucleus, mitochondria, endoplasmic reticulum and Golgi apparatus. However, fungi contain no chloroplasts or chlorophyll. Pigments in fungi cells produce bright colors.
Fungi have cell walls like plants that provides structural support. The rigid layers of fungal cell walls contain complex polysaccharides called chitin and glucans. In addition, fungi have cell membranes, but composed of ergosterol, a different chemical than other non-fungi eukaryotes. Most fungi are non-motile, but some fungi have flagella, such as (Chytridiomycota).
Unicellular fungi are called yeasts. The vegetative body of a fungi is called a thallus. Multicellular fungi produce threadlike hyphae. Dimorphic fungi can change from the unicellular state to the multicellular state.
Most fungi are multicellular and two distinct stages that they showcase include vegetative and reproductive stages. The vegetative stage consists of a tangle of hyphae, while the reproductive stage can be more obvious. The mass of hyphae is a mycelium and grows on a surface, in soil, decaying material, liquid, or on living tissue.
The honey mushroom (Armillaria solidipes) is considered the largest organism on earth, spreading across thousands of acres.
Most fungal hyphae are divided into separate cells by endwalls called septa or septum. Commonly tiny holes in the septa allow for the rapid flow of nutrients from cell to cell, known as perforated septa. In contrast, coenocytic hyphae are long, multinucleated cells that are not divided into compartments.
Fungi grow best in moist and slightly acidic environments, and in dark or light. Most fungi require oxygen respiration to survive (obligate aerobes). Some fungi do not use or can't use oxygen for respiration (obligate anaerobes). Yeasts are facultative anaerobes and grow best with oxygen, but can survive without oxygen.
Fungi are hetertrophic and use organic compounds for carbon and nutrients and do not use atmospheric carbon dioxide. Fungi cannot get nitrogen from the atmosphere by fixing and must obtain it from their diet. Fungi digest their food before ingestion with exoenzymes that are exported, digest the food, and then the fungi ingest the food. Food is stored in fungi as glycogen.
Most fungi are saprobes or saprophytes that obtain nutrients from decaying organic matter, mainly from plants. Carbon, nitrogen, and other elements are released into the environment and therefore fungi play a very important ecological role. Fungi can potentially be used in bioremediation of chemically damaged ecosystems.
Some fungi are parasitic with plants or animals, and can cause diseases in plants, animals, and humans. Many parasitic fungi possess haustoria, structures that penetrate the tissues of the host, release digestive enzymes within the host's body, and absorb the digested nutrients.
Fungi reproduce asexually by mitosis, sexually, or both. In both forms of reproduction, fungi produce many spores that disperse from the parent organism by either floating on the wind or hitching a ride on an animal.
Fungi reproduce asexually by fragmentation, budding, or producing spores. Fragments of hyphae can grow new colonies. Somatic cells in yeast form buds. During budding (an expanded type of cytokinesis), a bulge forms on the side of the cell, the nucleus divides mitotically, and the bud ultimately detaches itself from the mother cell.
The most common mode of asexual reproduction is through the formation of asexual spores, which are produced by a single individual thallus (through mitosis) and are genetically identical to the parent thallus. Spores allow fungi to expand their distribution and colonize new environments. These spores may be released from the parent thallus either outside or within a special reproductive sac called a sporangium.
Many types of asexual spores include conidiospores, which are unicellular or multicellular spores that are released directly from the tip or the side of the hypha. Other spores originate from fragmentation of hyphae, or bud off the vegetative parent cell. Sporangiospores are produced directly from a sporangium.
Sexual reproduction in fungi causes genetic variation in a population and often occurs as a result of harmful environmental conditions. Two mating types are produced during sexual reproduction. When both types are in the same mycelium, it is called homothallic, or self-fertile. Heterothallic mycelia require two different mycelia in sexual reproduction.
Three stages in fungal sexual reproduction include: plasmogamy, where two haploid cells fuse. Karyogamy is when the haploid nuclei fuse to form a diploid zygote nucleus. Then meiosis takes place in the gametangia organs, where gametes of different mating types are generated. The spores are then released into the environment.
In fungi classification, there are five major phyla established according to mode of sexual reproduction or molecular data. The five phyla of fungi are the Chytridiomycota (Chytrids), the Zygomycota (conjugated fungi), the Ascomycota (sac fungi), the Basidiomycota (club fungi) and Phylum Glomeromycota.
The only class in the Phylum Chytridiomycota is the Chytridiomycetes. These have chitin in their cell wall like all fungi. Most chytrids are unicellular, but some are multicellular with hyphae. Chytrids are the only fungi that have flagella. Gametes and diploid zoospores are produced with flagella. Both male and female gametes are flagellated. Chytrids usually live in aquatic environments, but some live on land. Some chytrids are parasites or saprobes.
Zygomycota is the conjugated fungi and includes bread molds. Most of these are saprobes and some are parasites. Zygomycetes have asexual and sexual phases in their life cycles. In the asexual phase, spores are produced from haploid sporangia by mitosis (not shown). In the sexual phase, plus and minus haploid mating types conjugate to form a heterokaryotic zygosporangium. Karyogamy then produces a diploid zygote. Diploid cells in the zygote undergo meiosis and germinate to form a haploid sporangium, which releases the next generation of haploid spores. Asexual sporangia grow at the end of stalks. The black tips of bread mold are the spore-containing sporangia.
Ascomycota fungi are known as the sac fungi because they form an ascus, (plural asci) a sac-like structure that contains haploid ascospores. The lifecycle of an ascomycete is characterized by the production of asci during the sexual phase. In each ascus, the four nuclei produced by meiosis divide once mitotically for a total of eight haploid ascospores. The haploid phase is the predominant phase of the life cycle in Ascomycetes.
Basidiomycota are known as the club fungi that feature club-shaped fruiting bodies called basidia which are swollen terminal cells of hyphae and are the reproductive organs of these fungi. These fungi produce mushrooms and have gill-like structures under the mushroom cap which are compacted hyphae where the basidia come from. These fungi grow in lawns and some grow on tree bark. Some of these fungi are edible and some are toxic. The lifecycle of a basidiomycete has sexual and asexual reproduction with haploid and dikaryotic mycelia. Haploid primary mycelia fuse to form a dikaryotic secondary mycelium, which is the dominant stage of the life cycle, and produces the basidiocarp, the familiar structure commonly recognized as a mushroom.
Some fungi do not display a sexual phase (asexual) and are more difficult to classify. These were once called deuteromycota. Now they are classified within other previously named fungi classifications. Most of these live on land and are commonly known as mold.
Glomeromycota is a new classification of fungi that are closely associated with the roots of trees and are asexual. Most members of this classification form arbuscular mycorrhizae, where the hyphae interact with the root cells forming a mutually beneficial association in which the plants supply the carbon source and energy in the form of carbohydrates to the fungus, and the fungus supplies essential minerals from the soil to the plant.
The Ecology of Fungi
The ecology of fungi is significant in most ecosystems on earth, and in particular dark, moist environments. Fungi can survive in extreme environments like tundra using symbiosis with organisms such as algae. Fungi serve as major decomposers and recyclers in the environment. In addition to humid and cool environments with organic matter, fungi live in seawater, human skin, and mucous membranes, aquatic environments, dry sandy soil, coral reefs, the forest floor.
Fungi work as decomposers and recyclers of organic matter in the food web. Fungi help circulate nitrogen and phosphorous in the environment. The ability of fungi to decompose organic matter is related to their digestive method, where exoenzymes digest nutrients, in addition to moisture that helps in decomposition. Fungi help replenish nutrients into the environment.
Symbiosis is a major part of the ecology of fungi. Mycorrhiza fungi have a symbiosis with vascular plant roots as both share nutrients that they would not be able to obtain otherwise. Ectomycorrhizae (“outside” mycorrhizae) depend on fungi enveloping the roots in a sheath (called a mantle). Hyphae grow from the mantle into the root and envelope the outer layers of the root cells in a network of hyphae called a Hartig net. Endomycorrhizae ("inside" mycorrhizae), also called arbuscular mycorrhizae, are produced when the fungi grow inside the root in a branched structure called an arbuscule (from the Latin for “little trees”). The fungal arbuscules penetrate root cells between the cell wall and the plasma membrane and are the site of the metabolic exchanges between the fungus and the host plant. Orchid seeds will not germinate without a mycorrhiza partner as they share nutrients. Endophytes are fungi that live inside tissue without damaging the host plant.
Lichens have a variety of colors and textures and can survive in a variety of environments, including unusual and harsh. Lichens grow on rocks, tree bark, and in the tundra ground. Lichens are not a single organism, but rather a mutual relationship where a fungus lives with a photosynthetic organism like eukaryotic alga or prokaryotic cyanobacteria and nutrients are shared in this relationship. Lichens are also a food source to some mammals and lichens also provide a shelter for some small invertebrates. Commercial applications exist with textiles.
Many invertebrates have symbiotic relationships with fungi, such as arthropods that use the fungus for protection, while the fungus obtains nutrients and a method of spore release. Leaf cutter ants and fungi have a symbiotic relationship where the ants collect portions of leaves where fungi also grow and consume the plant material. The ants consume the fungi.
Animals can carry fungi great distances, even through the waste of animals that feed on fungi and help complete the life cycle of certain fungi.
Parasitism is a symbiotic relationship where one member benefits at the expense of another. Pathogens cause disease in their host. Commensalism occurs when one member benefits without affecting the other. Many plant pathogen diseases that affect crops including fruits and vegetables are from fungi.
Mycosis is a fungal disease that results from infection and direct damage from the growth of the fungus in animals and humans. Mycotoxicosis is the poisoning of humans or animals from foods containing fungal toxins. Mycetismus is the result of ingestion of toxic mushrooms. Fungal infections commonly occur on animal skin. Systemic mycoses spread to internal organs and commonly enter the respiratory system.
Pathogenic fungi can be beneficial when they help control the population of insect pests. The mycorrhizal relationship of fungi with plant roots is very important to the productivity of farm land. Mushroom fungi are also a source of human and animal diet. Wild yeasts are used to ferment grains and fruits to produce alcoholic beverages. Antibiotics are naturally produced from fungi. Fungi have been used in genetics research
Fungi are living organisms that have the characteristics of both plants and animals and their classification is complicated. Fungi do not perform photosynthesis and are heterotrophic, relying on organic compounds for energy. Fungi have few characteristics shared with other organisms and an evolutionist lineage is difficult to make for these organisms.
Fungi cell walls, a characteristic of plants, are composed of chitin, a characteristic of animals. Fungi produce animal-like pigments. Also like animals, fungi store carbohydrates as glycogen. Fungi act like bacteria when they absorb nutrients across their surface and behave like decomposers by recycling nutrients and breaking down organic materials.
Some fungi reproduce only asexually while some reproduce both asexually and sexually with alternation of generations. Most fungi produce large amounts of spores, haploid cells that undergo mitosis to form multicellular haploid individuals.
Most terrestrial plants develop symbiotic relationships with fungi, such as when the plant roots and underground fungi parts share nutrients (mycorrhizae). Lichens form a symbiotic association with fungus and algae.
Fungi also cause major infectious diseases in plants, animals, and humans. But fungi have commercial applications in the food industry with yeast and fermentation, enzymes and antibiotics. The scientific study of fungi is called mycology.
Fungi are eukaryotes and have a membrane-bound nucleus, mitochondria, endoplasmic reticulum and Golgi apparatus. However, fungi contain no chloroplasts or chlorophyll. Pigments in fungi cells produce bright colors.
Fungi have cell walls like plants that provides structural support. The rigid layers of fungal cell walls contain complex polysaccharides called chitin and glucans. In addition, fungi have cell membranes, but composed of ergosterol, a different chemical than other non-fungi eukaryotes. Most fungi are non-motile, but some fungi have flagella, such as (Chytridiomycota).
Unicellular fungi are called yeasts. The vegetative body of a fungi is called a thallus. Multicellular fungi produce threadlike hyphae. Dimorphic fungi can change from the unicellular state to the multicellular state.
Most fungi are multicellular and two distinct stages that they showcase include vegetative and reproductive stages. The vegetative stage consists of a tangle of hyphae, while the reproductive stage can be more obvious. The mass of hyphae is a mycelium and grows on a surface, in soil, decaying material, liquid, or on living tissue.
The honey mushroom (Armillaria solidipes) is considered the largest organism on earth, spreading across thousands of acres.
Most fungal hyphae are divided into separate cells by endwalls called septa or septum. Commonly tiny holes in the septa allow for the rapid flow of nutrients from cell to cell, known as perforated septa. In contrast, coenocytic hyphae are long, multinucleated cells that are not divided into compartments.
Fungi grow best in moist and slightly acidic environments, and in dark or light. Most fungi require oxygen respiration to survive (obligate aerobes). Some fungi do not use or can't use oxygen for respiration (obligate anaerobes). Yeasts are facultative anaerobes and grow best with oxygen, but can survive without oxygen.
Fungi are hetertrophic and use organic compounds for carbon and nutrients and do not use atmospheric carbon dioxide. Fungi cannot get nitrogen from the atmosphere by fixing and must obtain it from their diet. Fungi digest their food before ingestion with exoenzymes that are exported, digest the food, and then the fungi ingest the food. Food is stored in fungi as glycogen.
Most fungi are saprobes or saprophytes that obtain nutrients from decaying organic matter, mainly from plants. Carbon, nitrogen, and other elements are released into the environment and therefore fungi play a very important ecological role. Fungi can potentially be used in bioremediation of chemically damaged ecosystems.
Some fungi are parasitic with plants or animals, and can cause diseases in plants, animals, and humans. Many parasitic fungi possess haustoria, structures that penetrate the tissues of the host, release digestive enzymes within the host's body, and absorb the digested nutrients.
Fungi reproduce asexually by mitosis, sexually, or both. In both forms of reproduction, fungi produce many spores that disperse from the parent organism by either floating on the wind or hitching a ride on an animal.
Fungi reproduce asexually by fragmentation, budding, or producing spores. Fragments of hyphae can grow new colonies. Somatic cells in yeast form buds. During budding (an expanded type of cytokinesis), a bulge forms on the side of the cell, the nucleus divides mitotically, and the bud ultimately detaches itself from the mother cell.
The most common mode of asexual reproduction is through the formation of asexual spores, which are produced by a single individual thallus (through mitosis) and are genetically identical to the parent thallus. Spores allow fungi to expand their distribution and colonize new environments. These spores may be released from the parent thallus either outside or within a special reproductive sac called a sporangium.
Many types of asexual spores include conidiospores, which are unicellular or multicellular spores that are released directly from the tip or the side of the hypha. Other spores originate from fragmentation of hyphae, or bud off the vegetative parent cell. Sporangiospores are produced directly from a sporangium.
Sexual reproduction in fungi causes genetic variation in a population and often occurs as a result of harmful environmental conditions. Two mating types are produced during sexual reproduction. When both types are in the same mycelium, it is called homothallic, or self-fertile. Heterothallic mycelia require two different mycelia in sexual reproduction.
Three stages in fungal sexual reproduction include: plasmogamy, where two haploid cells fuse. Karyogamy is when the haploid nuclei fuse to form a diploid zygote nucleus. Then meiosis takes place in the gametangia organs, where gametes of different mating types are generated. The spores are then released into the environment.
In fungi classification, there are five major phyla established according to mode of sexual reproduction or molecular data. The five phyla of fungi are the Chytridiomycota (Chytrids), the Zygomycota (conjugated fungi), the Ascomycota (sac fungi), the Basidiomycota (club fungi) and Phylum Glomeromycota.
The only class in the Phylum Chytridiomycota is the Chytridiomycetes. These have chitin in their cell wall like all fungi. Most chytrids are unicellular, but some are multicellular with hyphae. Chytrids are the only fungi that have flagella. Gametes and diploid zoospores are produced with flagella. Both male and female gametes are flagellated. Chytrids usually live in aquatic environments, but some live on land. Some chytrids are parasites or saprobes.
Zygomycota is the conjugated fungi and includes bread molds. Most of these are saprobes and some are parasites. Zygomycetes have asexual and sexual phases in their life cycles. In the asexual phase, spores are produced from haploid sporangia by mitosis (not shown). In the sexual phase, plus and minus haploid mating types conjugate to form a heterokaryotic zygosporangium. Karyogamy then produces a diploid zygote. Diploid cells in the zygote undergo meiosis and germinate to form a haploid sporangium, which releases the next generation of haploid spores. Asexual sporangia grow at the end of stalks. The black tips of bread mold are the spore-containing sporangia.
Ascomycota fungi are known as the sac fungi because they form an ascus, (plural asci) a sac-like structure that contains haploid ascospores. The lifecycle of an ascomycete is characterized by the production of asci during the sexual phase. In each ascus, the four nuclei produced by meiosis divide once mitotically for a total of eight haploid ascospores. The haploid phase is the predominant phase of the life cycle in Ascomycetes.
Basidiomycota are known as the club fungi that feature club-shaped fruiting bodies called basidia which are swollen terminal cells of hyphae and are the reproductive organs of these fungi. These fungi produce mushrooms and have gill-like structures under the mushroom cap which are compacted hyphae where the basidia come from. These fungi grow in lawns and some grow on tree bark. Some of these fungi are edible and some are toxic. The lifecycle of a basidiomycete has sexual and asexual reproduction with haploid and dikaryotic mycelia. Haploid primary mycelia fuse to form a dikaryotic secondary mycelium, which is the dominant stage of the life cycle, and produces the basidiocarp, the familiar structure commonly recognized as a mushroom.
Some fungi do not display a sexual phase (asexual) and are more difficult to classify. These were once called deuteromycota. Now they are classified within other previously named fungi classifications. Most of these live on land and are commonly known as mold.
Glomeromycota is a new classification of fungi that are closely associated with the roots of trees and are asexual. Most members of this classification form arbuscular mycorrhizae, where the hyphae interact with the root cells forming a mutually beneficial association in which the plants supply the carbon source and energy in the form of carbohydrates to the fungus, and the fungus supplies essential minerals from the soil to the plant.
The Ecology of Fungi
The ecology of fungi is significant in most ecosystems on earth, and in particular dark, moist environments. Fungi can survive in extreme environments like tundra using symbiosis with organisms such as algae. Fungi serve as major decomposers and recyclers in the environment. In addition to humid and cool environments with organic matter, fungi live in seawater, human skin, and mucous membranes, aquatic environments, dry sandy soil, coral reefs, the forest floor.
Fungi work as decomposers and recyclers of organic matter in the food web. Fungi help circulate nitrogen and phosphorous in the environment. The ability of fungi to decompose organic matter is related to their digestive method, where exoenzymes digest nutrients, in addition to moisture that helps in decomposition. Fungi help replenish nutrients into the environment.
Symbiosis is a major part of the ecology of fungi. Mycorrhiza fungi have a symbiosis with vascular plant roots as both share nutrients that they would not be able to obtain otherwise. Ectomycorrhizae (“outside” mycorrhizae) depend on fungi enveloping the roots in a sheath (called a mantle). Hyphae grow from the mantle into the root and envelope the outer layers of the root cells in a network of hyphae called a Hartig net. Endomycorrhizae ("inside" mycorrhizae), also called arbuscular mycorrhizae, are produced when the fungi grow inside the root in a branched structure called an arbuscule (from the Latin for “little trees”). The fungal arbuscules penetrate root cells between the cell wall and the plasma membrane and are the site of the metabolic exchanges between the fungus and the host plant. Orchid seeds will not germinate without a mycorrhiza partner as they share nutrients. Endophytes are fungi that live inside tissue without damaging the host plant.
Lichens have a variety of colors and textures and can survive in a variety of environments, including unusual and harsh. Lichens grow on rocks, tree bark, and in the tundra ground. Lichens are not a single organism, but rather a mutual relationship where a fungus lives with a photosynthetic organism like eukaryotic alga or prokaryotic cyanobacteria and nutrients are shared in this relationship. Lichens are also a food source to some mammals and lichens also provide a shelter for some small invertebrates. Commercial applications exist with textiles.
Many invertebrates have symbiotic relationships with fungi, such as arthropods that use the fungus for protection, while the fungus obtains nutrients and a method of spore release. Leaf cutter ants and fungi have a symbiotic relationship where the ants collect portions of leaves where fungi also grow and consume the plant material. The ants consume the fungi.
Animals can carry fungi great distances, even through the waste of animals that feed on fungi and help complete the life cycle of certain fungi.
Parasitism is a symbiotic relationship where one member benefits at the expense of another. Pathogens cause disease in their host. Commensalism occurs when one member benefits without affecting the other. Many plant pathogen diseases that affect crops including fruits and vegetables are from fungi.
Mycosis is a fungal disease that results from infection and direct damage from the growth of the fungus in animals and humans. Mycotoxicosis is the poisoning of humans or animals from foods containing fungal toxins. Mycetismus is the result of ingestion of toxic mushrooms. Fungal infections commonly occur on animal skin. Systemic mycoses spread to internal organs and commonly enter the respiratory system.
Pathogenic fungi can be beneficial when they help control the population of insect pests. The mycorrhizal relationship of fungi with plant roots is very important to the productivity of farm land. Mushroom fungi are also a source of human and animal diet. Wild yeasts are used to ferment grains and fruits to produce alcoholic beverages. Antibiotics are naturally produced from fungi. Fungi have been used in genetics research