Bio 102 Fungi L3A Modified PDF

BIO 102 FUNGI  INTRODUCTION The word fungus comes from the Latin word for mushrooms. The familiar mushroom is a reproductive structure used by many types of fungi, but there are also many fungi species that don't produce mushrooms at all. Being eukaryotes, a typical f...

BIO 102 FUNGI  INTRODUCTION The word fungus comes from the Latin word for mushrooms. The familiar mushroom is a reproductive structure used by many types of fungi, but there are also many fungi species that don't produce mushrooms at all. Being eukaryotes, a typical fungal cell contains a true nucleus and many membrane-bound organelles. The kingdom Fungi includes an enormous variety of living organisms collectively referred to as Eucomycota, or true Fungi. While scientists have identified about 100,000 species of fungi, this is only a fraction of the 1.5 million species of fungus likely present on Earth. Edible mushrooms, yeasts, black mold, and the producer of the antibiotic penicillin, Penicillium notatum, are all members of the kingdom Fungi, which belongs to the domain Eukarya. Fungi, once considered plant-like organisms, are more closely related to animals than plants.  Cont’d Like bacteria, fungi play an essential role in ecosystems because they are decomposers and participate in the cycling of nutrients by breaking down organic materials to simple molecules. Fungi often interact with other organisms, forming beneficial or mutualistic associations. For example most terrestrial plants form symbiotic relationships with fungi. The roots of the plant connect with the underground parts of the fungus forming mycorrhizae. Through mycorrhizae, the fungus and plant exchange nutrients and water, greatly aiding the survival of both species. Fungi are not capable of photosynthesis: they are heterotrophic because they use complex organic compounds as sources of energy and carbon. Some fungal organisms multiply only asexually, whereas others undergo both asexual reproduction and sexual reproduction with alternation of generations(life cycle in which subsequent generations alternate between diploid asexual and haploid sexual phases)  Cont’d Alternatively, lichens are an association between a fungus and its photosynthetic partner (usually an alga). Fungi also cause serious infections in plants and animals. In humans, fungal infections are generally considered challenging to treat. Unlike bacteria, fungi do not respond to traditional antibiotic therapy, since they are eukaryotes. Fungal infections may prove deadly for individuals with compromised immune systems. Fungi have many commercial applications. The food industry uses yeasts in baking, brewing, and cheese and wine making. Many industrial compounds are byproducts of fungal fermentation. Fungi are the source of many commercial enzymes and antibiotics.  CHARACTERISTICS OF FUNGI 1. Fungi are eukaryotic organisms. 2. They are non-vascular organisms. 3. They reproduce by means of spores, usually wind-disseminated 4. Depending on the species and conditions both sexual and asexual spores may be produced. 5. They are typically non-motile, although a few (e.g Chytrids) have a motile phase 6. Fungi exhibit the phenomenon of alteration of generation. 7. The vegetative body of the fungi may be unicellular or composed of microscopic threads called hyphae. 8. The structure of cell wall is similar to plants but chemically the fungi cell wall is composed of chitin. 9. Fungi are heterotrophic organisms.  Cont’d 10. Fungi digest the food first and then ingest the food, to accomplish this fungi produce exoenzymes. 11. Fungi store their food as glycogen. 12. Biosynthesis of chitin occurs in fungi. 13. The nuclei of the fungi are very small. 14. During mitosis the nuclear envelope is not dissolved. 15. Nutrition in fungi - they are saprophytes, or parasites or symbionts. 16. Reproduction in fungi is both by sexual and asexual means. Sexual state is referred to as teleomorph, asexual state is referred to as anamorph.  CELL STRUCTURE AND FUNCTION The most common body structures are multicellular filaments and single cells (yeasts). Some species grow as either filaments or yeasts; others grow as both. Fungal cells also contain mitochondria and a complex system of internal membranes, including the endoplasmic reticulum and Golgi apparatus. Unlike plant cells, fungal cells do not have chloroplasts or chlorophyll. Many fungi display bright colors arising from other cellular pigments, ranging from red to green to black.  GROWTH 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. Saccharomyces cerevisiae (baker’s yeast) and Candida species (the agents of thrush, a common fungal infection) are examples of unicellular fungi. 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. Fig.1 Structure of a Mushroom  The morphology of multicellular fungi enhances their ability to absorb nutrients. Fungi consist of mycelia, networks of branched hyphae adapted for absorption. Most fungi have cell walls made of chitin. Some unique fungi have specialized hyphae called haustoria that allow them to penetrate the tissues of their host and extract nutrients Fig 2: Specialized Hyphae in Mycorrhizal Fungi  Most fungal hyphae are divided into separate cells by end walls called septa (singular, septum) (Figure 3 ). 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 (Figure 3b) Fig.3 Fungal hyphae may be (a) Septate or (b) coenocytic  Cont’d Fungi thrive in environments that are moist and slightly acidic, and can grow with or without light. They vary in their oxygen requirement. Most fungi are obligate aerobes, requiring oxygen to survive. Other species such as the Chytridiomycota that reside in the rumen of cattle, are obligate anaerobes, this is because oxygen will disrupt their metabolism or kill them. Yeasts are intermediate, being facultative anaerobes. This means that they grow best in the presence of oxygen using aerobic respiration, but can survive using anaerobic respiration when oxygen is not available. The alcohol produced from yeast fermentation is used in wine and beer production.  NUTRITION Like animals, fungi are heterotrophs; they use complex organic compounds as a source of carbon, rather than fix carbon dioxide from the atmosphere and do not fix nitrogen from the atmosphere Like animals, they must obtain it from their diet, but 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. The smaller molecules produced by this external digestion are absorbed through the large surface area of the mycelium. They store polysaccharide as glycogen, rather than starch, as found in plants  Types of nutrition Saprophytic fungi 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 Parasitic fungi They absorb nutrients from the living cells of another organism called the host. Many parasitic fungi produced specialized hyphae called haustoria, which grow onto the hosts tissues and absorb their nutrients. Mutualistic fungi Some fungi live in a mutualistic relationship with another organism, such as a plant or algae. The mycelia of a particular fungus cover the root of a soybean plant. The fungus receives sugar from the host plant. The mycelia increase water uptake and mineral absorption for the host plant  REPRODUCTION Fungi reproduce sexually and/or asexually. Perfect fungi reproduce both sexually and asexually, while imperfect fungi reproduce only asexually (by mitosis). Fungal spores are smaller and lighter than plant seeds. The giant puffball mushroom bursts open and releases trillions of spores. The huge number of spores released increases the likelihood of landing in an environment that will support growth (Figure 4).  ASEXUAL REPRODUCTION Fungi reproduce asexually by fragmentation, budding, or producing spores. Somatic cells in yeast form buds and during budding (a 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 one parent only (through mitosis) and are genetically identical to that parent (Figure 5). Spores allow fungi to expand their distribution and colonize new environments. They may be released from the parent thallus either outside or within a special reproductive sac called a sporangium Figure 5: Fungi may have both asexual and sexual stages of reproduction CONT’D  CLASSIFICATIONS OF FUNGI Fungi have been classically characterized and classified by the following: appearance of their colony (color, size, etc), hyphal organization (septate or coenocytic), the structure and organization of reproduction spores. More recently, ribosomal RNA sequences are being used to further categorize these organisms. The kingdom Fungi contains five major phyla that were established according to their mode of sexual reproduction or us molecular data.  Cont’d The five true phyla of fungi are: 1. Chytridiomycota (Chytrids), 2. Zygomycota (conjugated fungi), 3. Ascomycota (sac fungi), 4. Basidiomycota (club fungi) 5. Deuteromycota (fungi imperfecti) The Deuteromycota is an informal group of unrelated fungi that all share a common character – they use strictly asexual reproduction. Note: “-mycota” is used to designate a phylum while “-mycetes” formally denotes a class or is used informally to refer to all members of the phylum  PHYLUM CHYTRIDIOMYCOTA The chytrids are the aquatic fungi. They are the causative agents of a deadly infection in frogs. Several species of chytrids are known to parasitize plants and insects, although many live on decaying plants and insect parts. The chytrids are very different from other fungi in many respects. They have flagellated spores and gametes, which is unique in the fungal kingdom. They are aquatic, some found in fresh water and marine. Chytrid cells have centrioles like animal cells do. Other phyla of fungi do not have centrioles. Although some chytrids are unicellular, many produce a mycelium much like other fungi. They are the oldest phylum of fungi and likely gave rise to the other phyla of fungi This gave scientists clues to fungal evolution, suggesting that fungi had their start in water, that they may be closely related to the animals  PHYLUM ZYGOMYCOTA The zygote-forming fungi commonly called “zygomycetes” include the bread molds. All members of this phylum produce a thick-walled zygote called a common black bread mold (Rhizopus nigricans) is an example of the zygote-forming fungi which are generally found on decaying food and other organic material. The name comes from zygosporangia, where resistant spherical spores are formed during sexual reproduction. They are mostly terrestrial in habitat, living in soil or on decaying plant or animal material and some are parasites of plants, insects, and small animals, while others form symbiotic relationships with plants. Zygomycete hyphae may be coenocytic, forming septa only where gametes are formed or to wall off dead hyphae  PHYLUM ASCOMYCOTA The sac fungi are the largest phylum of fungi, with at least 30,000 named species. They live in a wide variety of places, such as in the soil, in saltwater and fresh water, on dead plants and animals, and on animal feces. They are called sac fungi because their sexual spores, which occur in groups of eight, are enclosed in saclike structures called asci(singular: ascus). Their life cycles are similar to that of the club fungi. The members of the ascomycetes produce spores in a sac, which develops as a result of sexual reproduction. Asexual reproduction takes place when the fungus produces asexual spores called conidia (singular, conidium). The phylum includes organisms of considerable importance, such as the yeasts crucial to the baking and brewing industries, as well as numerous plant pathogens  PHYLUM BASIDIOMYCOTA Basidiomycota is one of two large phyla that, together with the Ascomycota, constitute the subkingdom Dikarya (often referred to as the "higher fungi") within the kingdom Fungi. These include these groups, mushrooms, puffballs, stinkhorns, bracket fungi, other polypores, jelly fungi etc. The mushroom is only a portion of the fungus and it is the fruiting body, specifically a basidiocarp, containing the sexually produced haploid basidiospores. These basidiospores are produced by a club-shaped basidium for which the group is named. Figure 8: The fruiting bodies of a basidiomycete form a ring in a meadow, commonly called “fairy ring.”  PHYLUM DEUTEROMYCOTA The Fungi imperfecti or imperfect fungi is also known as Deuteromycota, these are fungi which do not fit into the commonly established taxonomic classifications of fungi that are based on biological species concepts or morphological characteristics of sexual structures because their sexual form of reproduction has never been observed; hence the name "imperfect fungi." Only their asexual form of reproduction is known, meaning that this group of fungi produces their spores asexually, in the process called sporogenesis. The Deuteromycota were once considered a formal phylum of the kingdom Fungi. The term is now used only informally, to denote species of fungi that are asexually reproducing members of the fungal phyla Ascomycota and Basidiomycota. These fungi are among the most economically important, producing antibiotics (for example, one species of Penicilliumproduces penicillin). Others produce the citric acid used in the soft-drink industry; still others are used in the manufacture of cheese. Some are important pathogens of both plants and animals. TABLE 1: FUNGI PHYLA.  ECOLOGY OF FUNGI Fungi play a crucial role in the balance of ecosystems. They colonize most habitats on Earth, preferring dark, moist conditions and can thrive in seemingly hostile environments, such as the tundra, due to the symbiosis relationship with photosynthetic organisms like algae to produce lichens. Like bacteria, they are the major decomposers of nature and with their versatile metabolism, fungi break down organic matter, which would not otherwise be recycled HABITATS Fungi are primarily associated with humid and cool environments that provide a supply of organic matter; they colonize a surprising diversity of habitats, from seawater to human skin and mucous membranes. Chytrids are found primarily in aquatic environments. Fungi that parasitize coral reefs live in the ocean. However, most members of the Kingdom Fungi grow on the forest floor, where the dark and damp environment is rich in decaying debris from plants and animals. In these environments, fungi play a major role as decomposers and recyclers, making it possible for members of the other kingdoms to be supplied with nutrients and live  DECOMPOSERS AND RECYCLERS The food web would be incomplete without organisms that decompose organic matter. Some elements—such as nitrogen and phosphorus—are required in large quantities by biological systems, and yet are not abundant in the environment. The action of fungi releases these elements from decaying matter, making them available to other living organisms. Trace elements present in low amounts in many habitats are essential for growth, and would remain tied up in rotting organic matter if fungi and bacteria did not return them to the environment via their metabolic activity. MUTUALISTIC RELATIONSHIPS Symbiosis is the ecological interaction between two organisms that live together. When both members of the association benefit, the symbiotic relationship is called mutualistic. Fungi form mutualistic associations with many types of organisms, including cyanobacteria, algae, plants, and animals. i. FUNGUS/PLANT MUTUALISM One of the most remarkable associations between fungi and plants is the establishment of mycorrhizae.Mycorrhiza, which comes from the Greek words mycomeaning fungus and rhizomeaning root, refers to the association between vascular plant roots and their symbiotic fungi. In a mycorrhizal association, the fungal mycelia use their extensive network of hyphae and large surface area in contact with the soil to channel water and minerals from the soil into the plant. In exchange, the plant supplies the products of photosynthesis to fuel the metabolism of the fungus. Plants harbor harmless symbiotic endophytes that live inside leaves or other plant parts, these endophytes make toxins that deter herbivores and defend against pathogens  II. LICHENS Lichens display a range of colors and textures and can survive in the most unusual and hostile habitats. They cover rocks, gravestones, tree bark, and the ground in the tundra where plant roots cannot penetrate. Lichens can survive extended periods of drought, when they become completely desiccated, and then rapidly become active once water is available again. Lichens are not a single organism, but rather an example of a mutualism, in which a fungus (usually a member of the Ascomycota or Basidiomycota phyla) lives in close contact with a photosynthetic organism (a eukaryotic alga or a prokaryotic cyanobacterium).  Cont’d A lichen, or lichenized fungus, is actually two organisms functioning as a single, stable unit. Lichens comprise a fungus living in a symbiotic relationship with an alga or cyanobacterium (or both in some instances). There are about 17,000 species of lichen worldwide. The fungal component of a lichen is known as the "mycobiont," and the algal or cyanobacterial component is known as the “photobiont.” The scientific name for a lichen is the same as that of the mycobiont, regardless of the identity of the photobiont. For example, the fungus Sticta canariensis is capable of forming two different lichen associations with an alga and cyanobacterium, yet both lichens are referred to as Sticta canariensis.  Importance of Lichens Lichens are key players in a variety of environmental processes. For example, cyanobacterial photobionts participate in nitrogen fixation Lichens also contribute to a phenomenon known as biological weathering. The lichen mycobionts can break down rocks and release minerals by producing certain chemicals. Weathering can lead to the eventual disintegration of rocks which is also an essential step for the formation of primitive soils. When lichens decompose, the organic matter that is left behind, along with particles of rock and dust trapped by thalli provide material for the development of primitive soils. Finally, lichens are excellent indicators of pollution. According to the Forest Service lichens can absorb pollutants such as heavy metals, carbon and sulfur into their thalli. Extracting these pollutants gives an indication of the levels present in the atmosphere. This process is known as lichen biomonitoring.  Why form a dual organism? Fungi are incapable of photosynthesis because they lack the green pigment chlorophyll. They need to seek out outside sources of food. They absorb nutrition from organic substances, that is, carbon containing compounds such as carbohydrates, fats, or proteins. On the other hand, algae and cyanobacteria can conduct photosynthesis, similar to plants. So when a fungus, which is the dominant partner in this relationship, associates with an alga (usually from the green algae) or cyanobacterium to form a lichen, it is providing itself with constant access to a source of nourishment  Cyanobacteria Cyanobacteria also provide fungi with the additional benefit of nitrogen fixation. This is the biochemical reaction wherein atmospheric nitrogen is converted to ammonia, a more usable form of the element. In return, algae and cyanobacteria secure a Examples of the three types of lichens are shown here. (a) This is a crustose lichen found mostly on protected environment, marine rocks, Caloplaca marina. especially from (b) This is a foliose lichen, Flavoparmelia caperata. damaging ultraviolet (c) This is a fruticose lichen, Letharia vulpina, rays. which is sufficiently poisonous that it was once used to make arrowheads  iii. FUNGUS/ANIMAL MUTUALISM Fungi have evolved mutualisms with numerous insects in Phylum Arthropoda( jointed, legged invertebrates). The arthropods depend on the fungus for protection from predators and pathogens, while the fungus obtains nutrients and a way to disseminate spores into new environments. The association between species of Basidiomycota and scale insects is one example. The fungal mycelium covers and protects the insect colonies, while the scale insects foster a flow of nutrients from the parasitized plant to the fungus. Some fungi share their digestive services with animals and they help break down plant material in the guts of cows and other grazing mammals. Many species of ants and termites use the digestive power of fungi by raising them in “farms”  FUNGAL PARASITES AND PATHOGENS Parasitism describes a symbiotic relationship in which one member of the association benefits at the expense of the other. Both parasites and pathogens harm the host; however, the pathogen causes a disease, whereas the parasite usually does not. Commensalism occurs when one member benefits without affecting the other. Plant Parasites and Pathogens About 30% of known fungal species are parasites or pathogens, mostly on or in plants. Some fungi that attack food crops are toxic to humans, but animals are much less susceptible to parasitic fungi than are plants. The general term for a fungal infection in animals is mycosis The production of sufficient good-quality crops is essential to human existence.  Cont’d Plant diseases have ruined crops, bringing widespread famine. Many plant pathogens are fungi that cause tissue decay and eventual death of the host (Figure 10). In addition to destroying plant tissue directly, some plant pathogens spoil crops by producing potent toxins. Fungi are also responsible for food spoilage and the rotting of stored crops. For example, the fungus Clavicepspurpureacauses ergot, a disease of cereal crops (especially of rye). Although the fungus reduces the yield of cereals, the effects of the ergot's alkaloid toxins on humans and animals are of much greater significance. In animals, the disease is referred to as ergotism. The most common signs and symptoms are convulsions, hallucination, gangrene, and loss of milk in cattle. Aflatoxins are toxic, carcinogenic compounds released by fungi of the genus Aspergillus. Periodically, harvests of nuts and grains are tainted by aflatoxins, leading to massive recall of produce  Mycorrhizae Mycorrhizae literally translates to “fungus-root.” Mycorrhiza defines a generally mutually beneficial relationship between the root of a plant and a fungus that colonizes the plant root. In many plants, mycorrhiza are fungi that grow inside the plant’s roots, or on the surfaces of the roots. The plant and the fungus have a mutually beneficial relationship, where the fungus facilitates water and nutrient uptake in the plant, and the plant provides food and nutrients created by photosynthesis to the fungus. This exchange is a significant factor in nutrient cycles and the ecology, evolution, and physiology of plants.  Benefits of mycorrhizae Mycorrhiza associations are particularly beneficial in areas where the soil does not contain sufficient nitrogen and phosphorus, as well as in areas where water is not easily accessible. Because the mycorrhizal mycelia are much finer and smaller in diameter than roots and root hairs, they vastly increase the surface area for absorption of water, phosphorus, amino acids, and nitrogen—almost like a second set of roots. In more complex relationships, mycorrhizal fungi can connect individual plants within a mycorrhizal network. This network functions to transport materials such as water, carbon, and other nutrients from plant to plant, and even provides some type of defence communication via chemicals signifying an attack on an individual within the network. Studies have found that plants with mycorrhizal associations are more resistant to certain soil-borne diseases. In fact, mycorrhizal fungi can be an effective method of disease control. In the case of sheathing mycorrhiza, they create a physical barrier between pathogens and plant roots. In addition to disease resistance, mycorrhizal fungi can also impart to its host plant resistance to toxicity and resistance to insects, ultimately improving plant fitness and vigor.  ANIMAL AND HUMAN PARASITES AND PATHOGENS Fungi can affect animals, including humans, in several ways: A mycosis is a fungal disease that results from infection and direct damage. Fungi attack animals directly by colonizing and destroying tissues. Mycotoxicosis is the poisoning of humans (and other animals) by foods contaminated by fungal toxins (mycotoxins). Mycetismus describes the ingestion of preformed toxins in poisonous mushrooms. In addition, individuals who display hypersensitivity to molds and spores develop strong and dangerous allergic reactions. Fungal infections are generally very difficult to treat because, unlike bacteria, fungi are eukaryotes. Antibiotics only target prokaryotic cells, whereas compounds that kill fungi also harm the eukaryotic animal host. Many fungal infections are superficial; that is, they occur on the animal’s skin. Termed cutaneous (“skin”) mycoses, they can have devastating effects. For example, the decline of the world’s frog population in recent years may be caused by the chytrid fungus Batrachochytrium dendrobatidis, which infects the skin of frogs and presumably interferes with gaseous exchange  IMPORTANCE OF FUNGI IN HUMAN LIFE Although we often think of fungi as organisms that cause disease and rot in food, they are important to human life on many levels. 1. They influence the well-being of human populations on a large scale because they are part of the nutrient cycle in ecosystems. 2. As animal pathogens, fungi help to control the population of damaging pests. 3. These fungi are very specific to the insects they attack, and do not infect animals or plants. 4. The mycorrhizal relationship between fungi and plant roots is essential for the productivity of farm land. Without the fungal partner in root systems, 80–90 percent of trees and grasses would not survive. 5. We also eat some types of fungi. Mushrooms figure prominently in the human diet.  Cont’d 8. Molds of the genus Penicillium ripen many cheeses. 9. Fermentation of grains to produce beer and of fruits to produce wine is an ancient art that humans in most cultures have practiced for millennia. Wild yeasts are acquired from the environment and used to ferment sugars into CO2 and ethyl alcohol under anaerobic conditions. 10. Louis Pasteur was instrumental in developing a reliable strain of brewer’s yeast, Saccharomyces cerevisiae, for the French brewing industry in the late 1850s. This was one of the first examples of biotechnology patenting. 11. Antibiotics are naturally produced by fungi to kill or inhibit the growth of bacteria, limiting their competition in the natural environment. Important antibiotics, such as penicillin and the cephalosporins, are isolated from fungi. 12. Valuable drugs isolated from fungi include the immunosuppressant drug cyclosporine (which reduces the risk of rejection after organ transplant), the precursors of steroid hormones, and ergot alkaloids used to stop bleeding.  Economic Importance Of Fungi 1. Fungi are an important organism in human life. – They play an important role in medicine by yielding antibiotics, in agriculture by maintaining soil fertility, are consumed as food, and forms the basis of many industries. Let us have a look at some of the fields where fungi are really important. 2. Importance in Human Life – Fungi are very important to humans at many levels. They are an important part of the nutrient cycle in the ecosystem. They also act as pesticides. 3. Biological Insecticides – Fungi are animal pathogens. – Thus they help in controlling the population of pests. – These fungi do not infect plants and animals. – They attack specifically to some insects. – The fungus Beauveria bassiana is a pesticide that is being tested to control the spread of emerald ash borer. 4. Reusing These microbes along with bacteria bring about recycling of matter by decomposing dead matter of plants and excreta of animals in the soil, hence the reuse enriches the soil to make it fertile. The absence of activities of fungi can have an adverse effect on this on-going process by continuous assembly and piling of debris.  Cont’d 5. Importance in Medicine Metabolites of fungi are of great commercial importance. Antibiotics are the substances produced by fungi, useful for the treatment of diseases caused by pathogens. Antibiotics produced by actinomycetes and moulds inhibits the growth of other microbes. Apart from curing diseases, antibiotics are also fed to animals for speedy growth and to improve meat quality. Antibiotics are used to preserve freshly produced meat for longer durations. Penicillin is a widely used antibiotic, lethal for the survival of microbes. The reason it is extensively used is that it has no effect on human cells but kills gram-positive bacteria. Streptomycin, another antibiotic is of great medicinal value. It is more powerful than Penicillin as it destroys gram-negative entities. Yield-soluble antibiotics are used to check the growth of yeasts and bacteria and in treating plant diseases. Administration of Griseofulvin results in the absorption by keratinized tissues and are used to treat fungal skin diseases(ringworms). Ergot is used in the medicine and the vet industry. It is also used to control bleeding post-child-birth. LSD – Lysergic acid, is a derivative of ergot and is used in the field of psychiatry. Consuming fungi called Clavatia prevents cancer of the stomach.  Cont’d 6. Importance in Agriculture The fungi plant dynamic is essential in productivity of crops. Fungal activity in farmlands contributes to the growth of plants by about 70%. Fungi are important in the process of humus formation as it brings about the degeneration of the plant and animal matter. They are successively used in biological control of pests. Plant pests are used as insecticides to control activities of insects. For example – Empausa sepulchralis, Cordyceps melonhae. Use of fungal pesticides can reduce environmental hazards by a great extent. Fungi are also used in agricultural research. Some species of fungi are used in the detection of certain elements such as Copper and Arsenic in soil and in the production of enzymes. For instance, biological and genetic research on fungi named Neurospora led to the One Gene One Enzyme hypothesis. The fungi live in a symbiotic relationship with the plant roots known as mycorrhiza. These are essential to enhance the productivity of farmland. 80-90% of trees could not survive without the fungal partner in the root system. 7. Importance in Food industry Some fungi are used in food processing while some are directly consumed. For example – Mushrooms, which are rich in proteins and minerals and low in fat. Fungi constitute the basis in the baking and brewing industry. Alcoholic fermentation: They bring about fermentation of sugar by an enzyme called zymase producing alcohol which is used to make wine. Carbon dioxide- a byproduct in the process, is used as dry ice and also in the baking industry to make the dough (rising and lightening of dough). Saccharomyces cerevisiae is an important ingredient in bread, a staple food of humans for several years. It is also known as the baker’s yeast. Gibberellins: These are plant hormones produced by the fungus Gibberella fujikuroi which cause a disease of rice accompanied by abnormal elongation. Gibberellin is used to accelerate growth of several horticultural crops. Cheese Industry: Certain fungi popularly known as the cheese moulds play an important role in the refining of cheese. They give cheese a characteristic texture and flavour. Economic Importance of Fungi