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IV. Fungi KNOW RED STUFF A. Overview 1. General Characteristics - multicellular eukaryotes - heterotrophic - absorptive nutrition: excrete enzymes into environment and absorb the product of that digestion. They digest dead matter (decomposers) or live matter (pathogens), or may be symbiotes. IV. Fungi 2. Classification - Chytridiomycota - Zygomycota - Ascomycota - Basidiomycota Single celled members of these groups are all called “yeasts”. They are distinguished from protists based on a chitinous cell wall and absorptive (rather than phagocytic) nutrition. IV. Fungi 3. General Biology - The organism is composed of threadlike “hyphae” IV. Fungi 3. General Biology - The organism is composed of threadlike “hyphae” - The hypha can be coenocytic (without divisions) or septate (with incomplete cell walls between) IV. Fungi 3. General Biology - The organism is composed of threadlike “hyphae” - The hypha can be coenocytic (without divisions) or septate (with incomplete cell walls between) - These have a huge surface area/volume ratio for absorption. - The largest organisms known… 37 acres. IV. Fungi 4. Ecological Roles - decomposers: Fungi decompose lignin and cellulose, which most free-living bacteria can’t digest. IV. Fungi 4. Ecological Roles - decomposers: Fungi decompose lignin and cellulose, which most free-living bacteria can’t digest. * antibiotics IV. Fungi 4. Ecological Roles - decomposers: Fungi decompose liginin and cellulose, which most free-living bacteria can’t digest. * antibiotics - mycorrhizae: fungal symbiotes of certain plants. The fungus increases the absorbance area of roots dramatically, and passes water and nutrients to the plant. The plant feeds the fungus with glucose. IV. Fungi 4. Ecological Roles - decomposers: Fungi decompose liginin and cellulose, which most free-living bacteria can’t digest. * antibiotics - mycorrhizae: fungal symbiotes of certain plants. The fungus increases the absorbance area of roots dramatically, and passes water and nutrients to the plant. The plant feeds the fungus with glucose. - lichens – symbiote with alga IV. Fungi 4. Ecological Roles - decomposers: Fungi decompose liginin and cellulose, which most free-living bacteria can’t digest. * antibiotics - mycorrhizae: fungal symbiotes of certain plants. The fungus increases the absorbance area of roots dramatically, and passes water and nutrients to the plant. The plant feeds the fungus with glucose. - lichens – symbiote with alga - pathogens – Athlete’s foot, ringworm, yeast infections - parasites – entomophagous fungi IV. Fungi B. Zygomycetes - coenocytic hypha - asexual reproduction haploid hypha produces sporangia and releases spores. IV. Fungi B. Zygomycetes - sexual reproduction – hypha touch, and produce gametangia. Gametes produced inside – fusion into dikaryotic cells (2 nuclei). Each dikaryon then becomes diploid (fusion of nuclei and undergoes meiosis. Spores are released. - many are imporant mycorrhyzal symbionts. IV. Fungi C. Ascomycetes - septate hypha IV. Fungi C. Ascomycetes - septate hypha - characterized by production of spore-bearing “asci” IV. Fungi C. Ascomycetes - septate hypha - characterized by production of spore-bearing “asci” - baker’s yeast (levening and fermentation) - molds – pathogens of plants such as Aspergillus, Penicillium, Neurospora, Chestnut Blight, Dutch Elm disease, etc. IV. Fungi C. Ascomycetes - life cycle IV. Fungi D. Basidiomycetes - bear puffballs or mushrooms as fruiting bodies IV. Fungi D. Basidiomycetes - bear puffballs or mushrooms as fruiting bodies - haploid hyphae fuse in dikaryotic hyphae. IV. Fungi D. Basidiomycetes - bear puffballs or mushrooms as fruiting bodies - haploid hyphae fuse in dikaryotic hyphae. - these dikaryotic hyphae form the fruiting structure. IV. Fungi D. Basidiomycetes - bear puffballs or mushrooms as fruiting bodies - haploid hyphae fuse in dikaryotic hyphae. - these dikaryotic hyphae form the fruiting structure. - at the tip of each hyphae, the basidium forms, in which meiosis occurs to produce new haploid spores. - life cycle Characteristics of Fungal Hyphae: Septate versus Coenocytic Mycelium: Large, Visible Mass of Hyphae IMPORTANT DIVISIONS OF FUNGI 1. Deuteromycota u Not known to produce sexual spores. u Reproduce asexually. u Catch-all category for unclassified fungi: – Pneumocystis carinii: Causes pneumonia in AIDS patients. Leading cause of death in AIDS patients. Originally classified as a protozoan. – Candida albicans: Causes yeast infections of vagina in women. Opportunistic infections of mucous membranes in AIDS patients. Opportunistic Infection by Candida albicans in an AIDS Patient Source: Atlas of Clinical Oral Pathology, 1999 Life Cycle of Eupenicillium (Ascomycete) Reproduces Asexually and Sexually Severe nail infection with Trichophyton rubrum in a 37-year-old male AIDS patient. Source: Intern. J. Dermatol. 31(1992): 453. Disseminated Histoplasma capsulatum, skin infection. Source: Microbiology Perspectives, 1999. FUNGAL DISEASES Mycosis: Any fungal disease. Tend to be chronic because fungi grow slowly. Mycoses are classified into the following categories: I. Systemic mycoses: Fungal infections deep within the body. Can affect a number if tissues and organs. u Usually caused by fungi that live in the soil and are inhaled. Not contagious. u Examples: – Histoplasmosis (Histoplasma capsulatum): Initial infection in lungs. Later spreads through blood to most organs. Systemic Mycosis: Histoplasmosis Disseminated Histoplasma capsulatum, lung infection. Source: Microbiology Perspectives, 1999. FUNGAL DISEASES (Continued) II. Cutaneous mycoses: Fungal infections of the skin, hair, and nails. u Secrete keratinase, an enzyme that degrades keratin. u Infection is transmitted by direct contact or contact with infected hair (hair salon) or cells (nail files, shower floors). u Examples: – Ringworm (Tinea capitis and T. corporis) – Athlete’s foot (Tinea pedis) – Jock itch (Tinea cruris) Cutaneous Mycosis Ringworm skin infection: Tinea corporis Source: Microbiology Perspectives, 1999 Cutaneous Mycosis Candida albicans infection of the nails. Source: Microbiology Perspectives, 1999. FUNGAL DISEASES (Continued) III. Subcutaneous mycoses: Fungal infections beneath the skin. u Caused by saprophytic fungi that live in soil or on vegetation. u Infection occurs by implantation of spores or mycelial fragments into a skin wound. u Can spread to lymph vessels. IV. Superficial mycoses: Infections of hair shafts and superficial epidermal cells. Prevalent in tropical climates. FUNGAL DISEASES (Continued) Opportunistic mycoses: Caused by organisms that are generally harmless unless individual has weakened defenses: – AIDS and cancer patients – Individuals treated with broad spectrum antibiotics – Very old or very young individuals (newborns). u Examples: – Aspergillosis: Inhalation of Aspergillus spores. – Yeast Infections or Candidiasis: Caused mainly by Candida albicans. Part of normal mouth, esophagus, and vaginal flora. ECONOMIC IMPORTANCE OF FUNGI u 25-50% of harvested fruits and vegetables are damaged by fungi. u Fungal infections of plants are commonly called rots, rusts, blights, wilts, and smuts. – Phytophthora infestans: Caused great potato famine in mid1800s. Over 1 million people died from starvation in Ireland. Many immigrated to the U.S. u Beneficial fungi: – Candida oleophila: Prevents fungal growth on harvested fruits. – Saccharomyces cerevisiae: Used to make bread and wine. – Genetically engineered yeast strains are used to make proteins (Hepatitis B vaccine). – Taxomyces: Produces anticancer drug taxol. – Trichoderma: Produces cellulase. Used to make fruit juice.