Fungi: Types, Reproduction, and Ecology PDF

## Glomeromycetes * The glomeromycetes (phylum *Glomeromycota*) were once considered zygomycetes. * They are now classified in a separate clade. * Glomeromycetes form arbuscular mycorrhizae (*endomycorrhizae*). * Glomeromycetes grow independently of their plant partners, no evidence of sexual repro...

## Glomeromycetes * The glomeromycetes (phylum *Glomeromycota*) were once considered zygomycetes. * They are now classified in a separate clade. * Glomeromycetes form arbuscular mycorrhizae (*endomycorrhizae*). * Glomeromycetes grow independently of their plant partners, no evidence of sexual reproduction has so far ever been found in this group. They reproduce asexually, producing extremely large multinucleate spore. These large spores can persist in the soil until they come into contact with an uninfected root. ## Basidiomycetes * Basidomycetes (phylum *Basidiomycota*) include mushrooms, puffballs, and shelf fungi, mutualists, and plant parasites. * The phylum is defined by a clublike structure called a basidium, a transient diploid stage in the life cycle. * The basidiomycetes are also called club fungi. * In response to environmental stimuli, the mycelium reproduces sexually by producing elaborate fruiting bodies called *basidiocarps*. * Mushrooms are examples of basidiocarps. * The numerous basidia in a basidiocarp are sources of sexual spores called *basidiospores*. * Fairy rings starts when a spore lands in a meadow or a lawn and spreads its mycelium from that central region outward in a large circle, indicated by a circle of basidiocarps on the peripheral edge of the mycelium. Fungal enzymes are obviously strongest near the fungal filaments. ## Fungi play key roles in nutrient cycling, ecological interactions, and human welfare * Fungi are efficient decomposers. * They perform essential recycling of chemical elements between the living and nonliving world. * Fungi form mutualistic relationships with plants (their roots especially), algae, cyanobacteria, and animals. * Plants harbor harmless symbiotic *endophytes* that live inside leaves or other plant parts. * Endophytes make toxins that deter herbivores and defend against pathogens. * Leaf-cutter *Attini* ants that have domesticated fungi which they keep in underground gardens. * Leaf-cutter ants of Central and South America and southern U.S. cultivate *Lepiota* in special underground chambers. * Ants eat hyphae. * Fungi have a home. * Ants have *Streptomyces* bacteria that makes an antibiotic to kill off competing fungi. * The ants and their fungal gardens constitute a mutualistic partnership. ## Ecology of Fungi * A lichen is a symbiotic association between a photosynthetic microorganism (a cyanobacteria, green algae) and a fungus (a basidiomycete, or ascomycete) in which millions of photosynthetic cells are held in a mass of fungal hyphae. * *Endophytic fungi* live in the intercellular spaces inside plants. * Fungal endophytes in and on *Pinus strobus*. * Italian rye grass is more resistant to aphid feeding in the presence of endophytes. * Lichens are important pioneers and the first colonists on new rock and soil surfaces and have invaded the harshest habitats. * Lichens are sensitive to pollution, and their death can be a warning that air quality is deteriorating, lichens are used as bioindicators of air quality. * *Fruticose* lichen. * *Foliose* lichen. * *Crustose* lichen. * The algae can provide some carbon compounds, while cyanobacteria can provide nitrogen also, and fungi provide the environment for growth (especially water and minerals) and protection. * The fungi of lichens can reproduce sexually and asexually. * Asexual reproduction is by fragmentation or the formation of soredia, small clusters if hyphae with embedded algae. * In review: A lichen is a composite organism that consists of a fungal symbiont (an ascomycete or sometimes a basidiomycete fungus) and one or more photoautotrophs (green algae or cyanobacteria). * Most of these relationships are mutualistic although some scientists think that they are parasitic on their photosynthetic host. * *Ascomycetes* are found in all but about 20 of the 15,000 lichen species, the rest are basidiomycetes. ## Distinguishing Features of Morphology and Life Cycles | Fungal Phylum | Distinguishing Features of Morphology and Life Cycles | |-------------------|-----------------------------------------------------------------------------------------------------------| | *Zygomycota* | Resistant *zygosporangium* as sexual stage | | *Glomeromycota* | Form arbuscular mycorrhizae with plants | | *Basidiomycota* | Elaborate fruiting body (*basidiocarp*) containing many basidia that produce sexual spores (*basidiospores*) | | *Ascomycota* | Sexual spores (*ascospores*) borne internally in sacs called asci; ascomycetes also produce vast numbers of asexual spores (*conidia*) | ## Fungi as 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. * Animals are much less susceptible to parasitic fungi than are plants. * The general term for a fungal infection in animals is *mycosis*. * For example, *Coccidiomycosis* is a lung infection, *Candida (ascomycete)* is a systemic (blood borne) infection, *thrush (ascomycete)* can cause vaginal infections, *Athlete's foot* and *nail fungus (ascomycete)*, *Sporthrix* is a lymphatic infection, and *Ringworm (ascomycete)* is a skin mycosis. ## Fungal Parasites and Pathogens ## Fungal infections - Mycosis * Some fungi secrete toxins that make foods poisonous. * *Fusarium* – *Vomitoxin* * *Aspergillus flavus* – *Aflatoxin* - Carcinogenic compounds secreted from improperly stored grain and peanuts. ## Fungi * Fungi are: * Heterotrophic * Decomposers * Parasitic * Saprobic * Mutualistic * Not autotrophic or photoautotrophic ## Unikonts * The supergroup Unikonta includes animals, fungi, and some protists that are related to each other. * Amoebozoans. * Nucleariids. * Fungi. * Choanoflagellates. * Animals. * Excavata. * Chromalveolata. * Rhizaria. * Archaeplastida. ## Amoebozoans * Amoebozoans are amoeba that have lobe- or tube-shaped, rather than threadlike, pseudopodia. * They include gymnamoebas, entamoebas, and slime molds. * Slime molds, or mycetozoans, were once thought to be fungi. * Molecular systematics places slime molds in the clade Amoebozoa. * At one point in the life cycle, plasmodial slime molds form a mass called a *plasmodium* (not to be confused with malarial *Plasmodium*). * The *plasmodium* is undivided by membranes and contains many diploid nuclei. * It extends pseudopodia through decomposing material, engulfing food by phagocytosis. * Many species of plasmodial slime molds are brightly pigmented, usually yellow or orange. * Cellular slime molds form multicellular aggregates in which cells are separated by their membranes. * Cells feed individually, but can aggregate to form a fruiting body or in other terms an amoeboid stage that produces spores. * *Dictyostelium discoideum* is an experimental model for studying the evolution of multicellularity. ## Gymnamoebas * Gymnamoebas are common unicellular amoebozoans in soil as well as freshwater and marine environments. * Most gymnamoebas are heterotrophic and actively seek and consume bacteria and other protists. ## Entamoebas * Entamoebas are parasites of vertebrates and some invertebrates. * *Entamoeba histolytica* causes amebic dysentery in humans. ## Protists * Protists are found in diverse aquatic environments. * Some protist symbionts benefit their hosts. * Dinoflagellates nourish coral polyps that build reefs. * Hypermastigotes digest cellulose in the gut of termites. They are transmitted through proctodeal feeding (i.e., transmission of gut contents from anus of a donor to mouth of a receptor). ## Photosynthetic Protists * Many protists are important producers that obtain energy from the sun. * In aquatic environments, photosynthetic protists and prokaryotes are the main producers. <start_of_image> This document describes the characteristics, life cycles, and ecology of different types of fungi. It also discusses the roles of fungi in nutrient cycling and human welfare. The document also covers the characteristics and ecology of protists, particularly their roles in ecological relationships.