Zoospores are produced by one group of true Fungi Chytridiomycota , and by fungal-like organisms in Kingdom Straminipila and some slime molds see section "Fungal-like Organisms Studied by Plant Pathologists and Mycologists". Two types of flagella are known—the whiplash flagellum, which is directed backward, and the tinsel flagellum, which is directed forward.
The tinsel flagellum is only present in members of Kingdom Straminipila and does not occur in true fungi. The length of time zoospores are able to swim is determined by their endogenous energy reserves—zoospores cannot obtain food from external sources—and environmental conditions. Zoospores may exhibit chemotaxis—movement in response to a chemical gradient, e. At the end of its motile phase, the zoospore undergoes a process called encystment in which it either sheds or retracts the flagella and produces a cell wall.
The encysted zoospore, called a cyst, may germinate directly by the formation of a germ tube , or indirectly by the emergence of another zoospore. Zoospores are formed inside a sac-like structure called a zoosporangium by a process involving mitosis and cytoplasmic cleavage—similar to the formation of sporangiospores in sporangia. Depending upon the taxonomic group, zoospores emerge from the zoosporangium through breakdown of the zoosporangial wall, through a preformed opening in the wall covered with a cap called an operculum that flips back, or by a gelatinous plug that dissolves.
Chamydospores are survival propagules formed from an existing hyphal cell or a conidium that develops a thickened wall and cytoplasm packed with lipid reserves. The thickened cell walls may be pigmented or hyaline, and chlamydospores develop singly or in clusters, depending upon the fungus. Chlamydospores are passively dispersed, in most instances when the mycelium breaks down. Chlamydospores are formed by many different groups of fungi and are often found in aging cultures. Sclerotia sing.
Sclerotia contain food reserves, and are a type of survival propagule produced by a number of fungi in phyla Ascomycota and Basidiomycota; in some fungi, such as Rhizoctonia solani , they are the only type of propagule produced, whereas in fungi such as Claviceps purpurea and Sclerotinia sclerotiorum , they are overwintering structures that can germinate directly, or give rise to structures in which the meiospores are formed. The characteristics and diversity of the major phyla of true Fungi will be briefly described.
Selected representatives of the different phyla are introduced and, in many instances, illustrated. A generalized life cycle also is presented for each phylum that illustrates when plasmogamy cell fusion , karyogamy nuclear fusion and meiosis occur relative to each other, and the types of structures involved in these events. For more detailed information on members of Kingdom Fungi, recommended reading is provided at the end of this article.
Phylum Ascomycota is the largest group of fungi, with approximately 33, described species in three subphyla—Taphrinomycotina, Saccharomycotina, and Pezizomycotina. Members of this phylum reproduce sexually or meiotically Fig.
Many species of Ascomycota also or exclusively produce spores through an asexual or mitotic process; these spores, called conidia , exhibit a wide range of size, shape, color and septation among the different fungi in which they are formed. Conidia and ascospores are usually produced at different times of year, if ascospores are formed in the lifecycle. The existence of many Ascomycota having sexual and asexual states that are separated in time and space has long confused those new to mycology and plant pathology.
The asexual states of Ascomycota are especially important to the plant pathologist because they are more commonly encountered than the sexual state, and must be identified for control, quarantine, or other purposes.
Fungi that reproduce only via asexual means have been given various designations including deuteromycetes, fungi imperfecti, mitosporic fungi, conidial fungi, and anamorphic fungi. Subphylum Taphrinomycotina includes fungi that, with one known exception, do not form fruiting bodies—as examples, the fission yeast Schizosaccharomyces Fig. Subphylum Saccharomycotina contains approximately species of yeasts, most of which live as saprotrophs in association with plants and animals, but also including a small number of plant and animal pathogens Suh et al.
Asci are formed naked Fig. Yeasts traditionally have been important in the production of beer, wine, single cell protein and baker's yeast, but their role in industry has expanded to the production of citric acid, fuel alcohol, and riboflavin Kurtzman and Sugiyama Saccharomyces cerevisiae Fig. In , S. Subphylum Pezizomycotina is the largest group in the phylum, with more than 32, identified species that occupy a wide range of ecological niches, occurring as saprotrophs, parasites and mutualists with plants, animals and other fungi.
Three different types of asci occur in this subphylum, prototunicate, unitunicate and bitunicate. Prototunicate asci release ascospores by breakdown of the ascus wall, whereas in the unitunicate and bitunicate asci, the ascospores are forcibly discharged.
Bitunicate asci have an inner wall that balloons out from the outer wall prior to ascospore discharge, and in unitunicate asci the wall layers do not separate from each other. A wide range of fruiting bodies are formed by members of subphylum Pezizomycotina, including cleistothecia , chasmothecia , apothecia , perithecia and pseudothecia.
Stromata , hardened masses of hyphae on or in which perithecia or pseudothecia are formed, occur in some members of this subphylum. Cleistothecia sing. Common fungi that produce cleistothecia include the teleomorphic sexual states of Aspergillus and Penicillium Fig. Species of Aspergillus are important in the production of fermented foods and beverages, including soy sauce, miso and rice wine sake.
Some species of Aspergillus infect animals, causing a disease known as aspergillosis, and others produce mycotoxins. Aflatoxin is a potent carcinogen produced by A. The U. Food and Drug Administration established a strict limit of 20 parts per billion on aflatoxin levels in food, and the U. Penicillium species are also used in food production. For example, the blue veins in Roquefort and Gorgonzola cheeses are due to the growth and sporulation of particular species of Penicillium Fig.
The antibiotic penicillin, the "wonder drug" of the 20 th century, is produced by strains of P. Other species of Penicillium, such as P. Chasmothecia sing. The term is now used to refer to the fruiting bodies of the powdery mildew fungi Fig. Apothecia sing. Apothecia-forming fungi are also called "cup fungi" or discomycetes.
Some important groups of plant pathogens that form apothecia include species of Monilinia brown rot of peach; Figs. Perithecia sing. Most fungi producing perithecia also have unitunicate asci and are classified in Sordariomycetes , one of the largest classes of Ascomycota with more than 3, described species Zhang et al. These fungi have also been called pyrenomycetes. Members of this group are common in nearly all ecosystems, where they occur as saprotrophs, endophytes of plants, or pathogens of plants, animals and other fungi.
A large number of economically important plant pathogens belong to Sordariomycetes, including those that cause anthracnose diseases Glomerella cingulata , blasts Magnaporthe oryzae , rice blast pathogen , blights Cryphonectria parasitica , chestnut blight , ergot Claviceps purpurea , and Fusarium head blight scab of small grains Gibberella zeae. Pseudothecia sing. Asci form in locules openings inside vegetative fungal tissue called ascostroma ; this group has been called loculoascomycetes, but is now placed in class Dothideomycetes.
Other characteristics of Dothideomycetes include the formation of bitunicate asci, and many members of this group produce darkly pigmented, multiseptate asospores or conidia.
Similar to the Sordariomycetes, members of Dothideomycetes occur in a wide range of habitats as saprotrophs and associate with plants as pathogens, endophytes and growing on the surface of plants as epiphytes Schoch et al.
Examples of well-known plant pathogens belonging to this group include Venturia inaequalis apple scab; Fig. Most of the lichen-forming members of Ascomycota belong in class Lecanoromycetes. This is the largest class of fungi, with over 13, described species Miadlikowska et al. Most of the members of this class produce apothecial fruiting bodies Figs.
The lichen thallus produces a wide range of secondary metabolites that are of biological and ecological importance Miadlikowska et al. The lichen thallus is able to grow under a range of adverse conditions and some can survive for hundreds of years. Lichens are found in a wide range of habitats from the Arctic to Antarctic, including some species that can grow in aquatic and marine environments Webster and Weber Phylum Basidiomycota represents the second largest phylum of fungi, with nearly 30, described species.
Members of phylum Basidiomycota produce basidiospores on a typically club-shaped structure called a basidium Fig. Characteristic of the mycelium of many members of Basidiomycota is the presence of clamp connections Figs. Three main lineages are recognized in phylum Basidiomycota: subphyla Ustilaginomycotina, Pucciniomycotina, and Agaricomycotina Blackwell et al.
Ustilaginomycotina and Pucciniomycotina are composed mostly of plant parasitic species, known as smut and rust fungi, respectively, characterized by a state that produces thick-walled teliospores Figs.
The most extensively studied members of Ustilaginomycotina are species of Tilletia and Ustilago. Ustilago maydis , which causes corn smut Fig. These structures eventually become filled with dark teliospores and are considered a delicacy in Mexico called "cuitlacoche. Subphylum Pucciniomycotina include the group of plant parasites called rust fungi. The rust fungi are remarkable in having as many as five distinct types of spores in a single life cycle spermatia, aeciospores, urediniospores, teliospores, and basidiospores Fig.
Rust fungi that produce all five spore states are macrocyclic , those that do not form uredinospores are demicyclic , and those that do not form urediniospores and aeciospores are microcyclic. Rust fungi may complete the life cycle on one host autoecious rusts or require two unrelated alternate hosts for completion of the life cycle heteroecious rusts.
The most widely cited example of a macrocyclic, heteroecious rust is Puccinia graminis black stem rust , which forms two spore states uredinia and telia on cultivated wheat Fig. The fifth state, the probasidium producing basidiospores, is formed upon germination of the teliospores Fig. Subphylum Agaricomycotina, previously known as the Hymenomycetes, includes the morphologically diverse group of fungi that produce basidia in various types of fruiting bodies Fig. This group includes the fungi commonly known as mushrooms Fig.
Many species are saprotrophic, utilizing dead plant material including woody substrates. Some of these saprotrophic species are cultivated for food, for example, the common button mushroom Agaricus bisporus , oyster mushrooms Pleurotus ostreatus , and shiitake Lentinula edodes. Other members of this group are important ectomycorrhizal fungi, forming mutualistic associations with the roots of a wide range of trees. Some fruiting bodies produced by ectomycorrhizae are considered choice edibles, for example, chanterelles Cantharellus cibarius and other species , porcini Boletus edulis , and the American matsutake Tricholoma magnivelare Fig.
A few members of this group are economically important plant parasites, e. This is an ancient group of fungi, recognizable in the fossil record dating back at least million years. Some AM fungi also produce storage structures inside plant roots called vesicles. Endomycorrhizal fungi produce an extensive network of hyphae outside the roots extraradical hyphae.
The extraradical hyphae act like an extension of the plant roots, increasing the plant's access to water and soil minerals, particularly phosphorous and nitrogen. The fungus is also able to access phosphate not otherwise available to plants, for example from organic matter by production of acid phosphatases. Spores may be formed singly or in clusters, and the mycelium of AM fungi is coenocytic.
Sexual reproduction is not known to occur in this phylum. The feature that is shared by all members of this phylum is the formation of zoospores with one posteriorly directed, whiplash flagellum. A few chytrids are economically important plant pathogens, e.
As previously noted, the frog chytrid, Batrachochytrium dendrobatidis , has been implicated as a major factor in population declines of frogs and other amphibians around the world Berger et al. This phylum contains approximately identified species divided amongst two ecologically distinct classes, Zygomycetes and Trichomycetes White et al. The most commonly encountered Zygomycetes are members of orders Mortierellales and Mucorales.
Many members of these two orders are saprotrophs with rapidly growing, coenocytic mycelium. The sexual reproductive state is the zygospore Fig. Members of order Mucorales, commonly called mucoraceous fungi, are common in soil, dung, plant material, and other types of organic matter. Some mucoraceous fungi are plant or animal pathogens, and others are used in the production of Asian foods such as tempeh.
Species of Mucor and Rhizopu s Fig. Species of Pilobolus Figs. Other Zygomycetes are associated with animals. For example, some species of Rhizopus and Mucor cause zygomycosis in immunocompromised humans.
Entomophthorales, as the name suggests, include parasites of insects and other animals. Members of class Trichomycetes live in the guts of insects, millipedes, and crustaceans, but cause little or no harm to their hosts. Oomycetes are fungal-like organisms that form zoospores with two flagella—a whiplash flagellum that is directed backwards and propels the zoospore, and a tinsel flagellum adorned with hairs that is directed forward, pulling the zoospore.
The cell walls of Oomycetes contain cellulose, rather than chitin, and glucans. Kirk et al. Another characteristic of Oomycetes is the formation of an oospore , a thick-walled, resistant propagule which is the result of sexual reproduction.
Oomycetes belong in Kingdom Straminipila, also known as Chromista. In addition to Oomycetes, this kingdom includes diatoms, golden and brown algae, a type of algae called cryptomonads, and two other groups of organisms studied by mycologists in phyla Labyrinthulomycota and Hyphochytriomycota. The tinsel type flagellum is a characteristic of all members of Kingdom Straminipila, hence it is also called a straminipilous flagellum.
Oomycetes include some of our most devastating plant pathogens. These fungal-like organisms have changed the course of history. Consider 19 th century Ireland; life was hard for the millions of Irish in the s who relied almost entirely upon the "lumper" potatoes they grew on leased quarter-acre plots for food and rent.
It's said that the stomachs of these "cottiers" were distended from eating up to fourteen pounds of potatoes each day Large Then, in , the potatoes began to rot from a malady known as "Potato Murrain," what we now call late blight of potato. Without potatoes, 4.
Over the next 15 years, one million Irish died from the famine, and one and a half times that number fled Ireland. Late blight is caused by Phytophthora infestans , and this oomycete continues to be a major pathogen in potato production, although we now have the ability to control it through the application of fungicides.
A number of other important plant pathogens are found among the Oomycetes, but only a few will be mentioned here. Phytophthora ramorum causes sudden oak death and ramorum blight. Pythium species cause damping-off diseases under extremely wet conditions. Seedlings are particularly vulnerable to attack by damping-off pathogens because their tissues are soft and easily invaded. Seedlings may be killed before or after they emerge from the soil. Downy mildews Peronosporales are biotrophic Oomycetes that are characterized by the formation of white, downy sporangiophores on the surface of infected hosts.
The white rusts Albugo spp. Albugo species parasitize crucifers and produce blister-like pustules filled with sporangia, which will germinate to produce motile zoospores. White rusts can also cause infected stems to grow in a contorted or twisted manner.
Members of Saprolegniales are called water molds. Many of these produce fast-growing, robust hyphae on organic matter in aquatic environments, but some species of Saprolegnia are parasitic on fish and fish eggs.
Labyrinthulids phylum Labyrinthulomycota , a small group of Straminipila, include organisms that cause rapid blight of turf grass and the wasting disease of eelgrass. Labyrinthulids have a unique manner of movement—their microscopic, football-shaped cells produce an ectoplasmic net through which the cells glide. The slow, gliding movement of the cells within the ectoplasmic net can be observed under the microscope.
Hyphochytrids phylum Hyphochytridomycota , Kingdom Straminipila are similar to chytrids in appearance, as their name suggests, and produce zoospores with a single anterior tinsel flagellum.
Hyphochytrids are one of the smallest groups of fungal-like organisms, both in size and in number of species with only 23 known. Some hyphochytrids are known to parasitize algae, spores of AM fungi, and oospores of Oomycetes. Slime molds are organisms that have a trophic feeding stage in their life cycle that lacks a cell wall, either uninucleate amoeba or multinucleate plasmodium.
The lack of a cell wall facilitates engulfment of food, in contrast to true fungi that must absorb their nutrients through a cell wall. The slime molds are now included in the Amoebozoa Adl et al. Four groups of slime molds are recognized—plasmodial slime molds Myxomycota , cellular slime molds Dictyosteliomycota and Acrasiomycota and endoparasitic slime molds Plasmodiophoromycota. We will briefly cover plasmodial slime molds and endoparasitic slime molds.
For information on cellular slime molds, refer to one of the introductory mycology texts listed below Recommended Further Reading. The plasmodial slime molds are most commonly found in temperate forests, where they occur on plant litter, tree bark, and other types of plant material.
The most conspicuous stage of the plasmodial slime mold is the fruiting structures, called sporophores Alexopoulos et al. One of the most common slime molds in temperate regions is Fuligo septica.
The sporophores of this slime mold are often found in ornamental bark and mulch, and look more like an animal's vomit than the fruiting structure of a living organism, thus earning the nickname: "dog vomit slime" Fig.
The presence of slime molds in landscaping Fig. Members of phylum Plasmodiophoromycota are biotrophic parasites that produce their plasmodial stage inside the cells of plants, algae, diatoms, and Oomycetes.
Several members of this phylum are economically important plant parasites, including Plasmodiophora brassicae , which causes clubroot of crucifers Fig. Polymyxa graminis is a vector for soilborne wheat mosaic virus, an economically important disease of wheat.
Members of this phylum produce cysts inside host cells; the cysts are released when the plant tissue breaks down, and germinate to release a zoospore that infects the host by injecting its cytoplasm into a host cell.
Infected host tissue may become greatly swollen as in clubroot of crucifers. As we have seen, a fungus is a eukaryotic organism that absorbs nutrients through its cell walls and generally reproduces by sporesTrue fungi belong to Kingdom Fungi, and other fungal-like organisms are placed in phyla outside the Kingdom Fungi. Most fungi consist of a hyphal thallus that allows these organisms to colonize and exploit many different substrates and fill various ecological niches, as parasites, pathogens, mutualists, saprotrophs and decomposers.
Fungi and fungal-like organisms survive and reproduce via a huge diversity of spore types, characteristic of each taxonomic group. This introduction has provided some basic information on reproduction, nutrient acquisition, and roles in the ecosystem, but much more information is available see Recommended Further Reading and the References. Fungi are fascinating in and of themselves, but they are also critically important to humans in both detrimental and beneficial ways. They are mostly aquatic, and their gametes are the only fungal cells known to have flagella.
They reproduce both sexually and asexually; the asexual spores are called zoospores. Zygomycota conjugated fungi produce non-septate hyphae with many nuclei. Their hyphae fuse during sexual reproduction to produce a zygospore in a zygosporangium. Ascomycota sac fungi form spores in sacs called asci during sexual reproduction. Asexual reproduction is their most common form of reproduction. In the Basidiomycota club fungi , the sexual phase predominates, producing showy fruiting bodies that contain club-shaped basidia, within which spores form.
Most familiar mushrooms belong to this division. Glomeromycota form tight associations called mycorrhizae with the roots of plants. Figure Which of the following statements is true? Members of which phylum produce a club-shaped structure that contains spores?
Members of which phylum establish a successful symbiotic relationship with the roots of trees? A scientist discovers a new species of fungus that introduces genetic diversity during reproduction by creating a diploid zygote. This new species cannot belong to which modern phylum of fungi? What is the advantage for a basidiomycete to produce a showy and fleshy fruiting body? By ingesting spores and disseminating them in the environment as waste, animals act as agents of dispersal.
The benefit to the fungus outweighs the cost of producing fleshy fruiting bodies. For each of the four groups of perfect fungi Chytridiomycota, Zygomycota, Ascomycota, and Basidiomycota , compare the body structure and features, and provide an example.
Chytridiomycota Chytrids may have a unicellular or multicellular body structure; some are aquatic with motile spores with flagella; an example is the Allomyces. Zygomycota conjugated fungi have a multicellular body structure; features include zygospores and presence in soil; examples are bread and fruit molds. Ascomycota sac fungi may have unicellular or multicellular body structure; a feature is sexual spores in sacs asci ; examples include the yeasts used in bread, wine, and beer production.
Basidiomycota club fungi have multicellular bodies; features includes sexual spores in the basidiocarp mushroom and that they are mostly decomposers; mushroom-producing fungi are an example. Skip to content Fungi. Learning Objectives By the end of this section, you will be able to do the following: Identify fungi and place them into the five major phyla according to current classification Describe each phylum in terms of major representative species and patterns of reproduction.
Fungal phyla. The chytrid Batrachochytrium dendrobatidis is seen in these light micrographs as transparent spheres growing on a a freshwater arthropod water mite and b algae. This chytrid causes skin diseases in many species of amphibians, resulting in species decline and extinction.
Zygomycete life cycle. 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. Ascomycota: The Sac Fungi The majority of known fungi belong to the Phylum Ascomycota , which is characterized by the formation of an ascus plural, asci , a sac-like structure that contains haploid ascospores.
Visual Connection. Ascomycete life cycle. 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.
The bright field light micrograph shows ascospores being released from asci in the fungus Talaromyces flavus var.
Most members of the kingdom Fungi are nonmotile. The vegetative body of a fungus is a unicellular or multicellular thallus. Dimorphic fungi can change from the unicellular to multicellular state depending on environmental conditions. Unicellular fungi are generally referred to as yeasts. Example of a unicellular fungus : Candida albicans is a yeast cell and the agent of candidiasis and thrush. This organism has a similar morphology to coccus bacteria; however, yeast is a eukaryotic organism note the nucleus.
Most fungi are multicellular organisms. They display two distinct morphological stages: the vegetative and reproductive. The vegetative stage consists of a tangle of slender thread-like structures called hyphae singular, hypha , whereas the reproductive stage can be more conspicuous.
The mass of hyphae is a mycelium. It can grow on a surface, in soil or decaying material, in a liquid, or even on living tissue. Example of a mycelium of a fungus : The mycelium of the fungus Neotestudina rosati can be pathogenic to humans. The fungus enters through a cut or scrape and develops a mycetoma, a chronic subcutaneous infection. Most fungal hyphae are divided into separate cells by endwalls called septa singular, septum a, c.
In most phyla of fungi, tiny holes in the septa allow for the rapid flow of nutrients and small molecules from cell to cell along the hypha. They are described as perforated septa. The hyphae in bread molds which belong to the Phylum Zygomycota are not separated by septa. Instead, they are formed by large cells containing many nuclei, an arrangement described as coenocytic hyphae b.
Fungi thrive in environments that are moist and slightly acidic; they can grow with or without light. A bright field light micrograph of c Phialophora richardsiae shows septa that divide the hyphae. Like animals, fungi are heterotrophs: they use complex organic compounds as a source of carbon, rather than fix carbon dioxide from the atmosphere as do some bacteria and most plants. In addition, fungi do not fix nitrogen from the atmosphere. Like animals, they must obtain it from their diet.
However, unlike most animals, which ingest food and then digest it internally in specialized organs, fungi perform these steps in the reverse order: digestion precedes ingestion. First, exoenzymes are transported out of the hyphae, where they process nutrients in the environment.
Then, the smaller molecules produced by this external digestion are absorbed through the large surface area of the mycelium. As with animal cells, the polysaccharide of storage is glycogen rather than the starch found in plants. Fungi are mostly saprobes saprophyte is an equivalent term : organisms that derive nutrients from decaying organic matter.
They obtain their nutrients from dead or decomposing organic matter, mainly plant material. Fungal exoenzymes are able to break down insoluble polysaccharides, such as the cellulose and lignin of dead wood, into readily-absorbable glucose molecules.
The carbon, nitrogen, and other elements are thus released into the environment. Because of their varied metabolic pathways, fungi fulfill an important ecological role and are being investigated as potential tools in bioremediation. Some fungi are parasitic, infecting either plants or animals.
Fungi can reproduce asexually by fragmentation, budding, or producing spores, or sexually with homothallic or heterothallic mycelia. Perfect fungi reproduce both sexually and asexually, while imperfect fungi reproduce only asexually by mitosis.
Most species multiply by asexual and sexual reproductive cycles and display an alternation of generations. In one group of fungi, no sexual cycle has been identified. Sexual reproduction involves plasmogamy the fusion of the cytoplasm , followed by karyogamy the fusion of nuclei. Following these processes, meiosis generates haploid spores.
What are the evolutionary advantages for an organism to reproduce both asexually and sexually? Asexual reproduction is fast and best under favorable conditions. Sexual reproduction allows the recombination of genetic traits and increases the odds of developing new adaptations better suited to a changed environment. Compare plants, animals, and fungi, considering these components: cell wall, chloroplasts, plasma membrane, food source, and polysaccharide storage.
Animals have no cell walls; fungi have cell walls containing chitin; plants have cell walls containing cellulose. Chloroplasts are absent in both animals and fungi but are present in plants.
Animal plasma membranes are stabilized with cholesterol, while fungi plasma membranes are stabilized with ergosterol, and plant plasma membranes are stabilized with phytosterols. Animals obtain N and C from food sources via internal digestion. Fungi obtain N and C from food sources via external digestion. Plants obtain organic N from the environment or through symbiotic N-fixing bacteria; they obtain C from photosynthesis.
Animals and fungi store polysaccharides as glycogen, while plants store them as starch. Why is the large surface area of the mycelium essential for nutrient acquisition by fungi? Fungi break down decaying matter in their environment to serve as their food source. Since the digestion occurs externally, the large mycelium can secrete exoenzymes over a large area.
The fungi must be able to absorb the small molecules released by digestion, so having a large surface area increases the amount of digested molecules that are captured by the fungi. Skip to content Fungi. Learning Objectives By the end of this section, you will be able to do the following: List the characteristics of fungi Describe the composition of the mycelium Describe the mode of nutrition of fungi Explain sexual and asexual reproduction in fungi.
Career Connection. Cell Structure and Function Fungi are eukaryotes, and as such, have a complex cellular organization. The poisonous Amanita muscaria is native to temperate and boreal regions of North America. Growth The vegetative body of a fungus is a unicellular or multicellular thallus. Candida albicans. Candida albicans is a yeast cell and the agent of candidiasis and thrush. This organism has a similar morphology to coccus bacteria; however, yeast is a eukaryotic organism note the nucleus.
A fungal mycelium. The mycelium of the fungus Neotestudina rosati can be pathogenic to humans. The fungus enters through a cut or scrape and develops a mycetoma , a chronic subcutaneous infection.
Fungal hyphae. A bright field light micrograph of c Phialophora richardsiae shows septa that divide the hyphae. Nutrition Like animals, fungi are heterotrophs; they use complex organic compounds as a source of carbon, rather than fix carbon dioxide from the atmosphere as do some bacteria and most plants.
Puffball and spores. The a giant puffball mushroom releases b a cloud of spores when it reaches maturity. Budding in Histoplasma.
The dark cells in this bright field light micrograph are the pathogenic yeast Histoplasma capsulatum, seen against a backdrop of light blue tissue. Histoplasma primarily infects lungs but can spread to other tissues, causing histoplasmosis, a potentially fatal disease. Generalized fungal life cycle. Fungi may have both asexual and sexual stages of reproduction.
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