Intro to fungi_presentation - fall 2008
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Intro to fungi_presentation - fall 2008

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  • Most enzyme release (and absorption) at tips Proteins and other materials synthesized by the entire mycelium are channeled by cytoplasmic streaming to the tips of the extending hyphae.
  • Chitin is the same material used by Arthropods (Insects, crabs, etc.) in their exoskeletonsa Nuclei of fungi are hard to see without stains
  • Half of the mushroom-forming fungi (basidiomycota) form mycorrhizas with trees Some people think that the spongy tissue in roots evolved as a place where fungi could invade to form early links with plants that helped them survive the harsh life on early earth
  • 4 of the regions where mycorrhizas are found are circled. These are “ecto” because the hyphae remain outside the root cells (though they extend inside the root)
  • Thallus is a plant-like body that doesn’t have roots, stems or leaves Thallus doesn’t look like either partner Dual nature of thalli was not fully understood until early 1900’s Fungus gives the name to the lichen (by agreement) Fungus usually, but not always, an Ascomycote (in 8+ independent orders) Algae green. If bluegreen bacteria present, lichens fix nitrogen (turn atmospheric nitrogen into amino acid nitrogen in proteins)
  • The nature of lichen symbiosis is may also be described as mutual exploitation instead of mutual benefit. Lichens live in environments where neither fungi nor algae could live alone. While the fungi do not not grow alone in the wild, some (but not all) lichen algae occur as free-living organisms. If cultured separately, the fungi do not produce lichen compounds and the algae do not “leak” carbohydrate from their cells. In some lichens, the fungus invades algal cells with haustoria and kills some of them, but not as fast as the algae replenish its numbers by reproduction. Lobaria oregana prefers old-growth conifer canopies in forests with clean air.
  • Fungi reproduce by releasing spores that are produced either sexually or asexually. The output of spores from one reproductive structure is enormous, with the number reaching into the trillions. Dispersed widely by wind or water, spores germinate to produce mycelia if they land in a moist place where there is food.
  • Fungal mycelia can be huge, but they usually escape notice because they are subterranean. One giant individual of Armillaria ostoyae in Oregon is 3.4 miles in diameter and covers 2,200 acres of forest, It is at least 2,400 years old, and weighs hundreds of tons. (Actually noone has seen this of this extent – but cultures have been taken from soil over that area and all isolates have been found to be the same individual) Ten cubic centimeters of rich organic soil may have fungal hyphae with a surface area of over 300 cm 2
  • Molecular studies indicate that animals, not plants, are the closest relatives of fungi. Both Animals and Fungi are related most closely to a group of Protists known as the choanoflagellates (collar flagellates) Kingdom began in ocean during Precambrian (Late Proterozoic era) More than 100,000 species of fungi are known and mycologists estimate that there are actually about 1.5 million species worldwide.
  • The phyla of fungi are determined by 1. motility of spores 2. nature of sexual stage Fungi moved onto land with the plants in the Early Paleozoic Much of the evolution of fungi was in conjunction with the evolution of plants and plant parts For example, when roots evolved, fungi were there and helped (mycorrhizas) When wood evolved, fungi evolved to take advantage of it Other evolutionary changes related to animals
  • Classified in CMR as true fungi (because of their molecular relationships) Remainder of the phyla are almost exclusively terrestrial (a few molds on wet plant material)
  • Most of the 600 zygomycote, or zygote fungi , are terrestrial, living in soil or on decaying plant and animal material. Asexual reproduction in sporangia One zygomycote group form mycorrhizas , mutualistic associations with the roots of plants.
  • Mycologists have described over 60,000 species of ascomycetes, or sac fungi . Ascomycota tend to grow from spore to spore in one year and relate well to living plant tissues There is diverse form in the growth and fruiting structures – yeasts to morels, many intermediate (and small) Asexual reproduction by conidia (externally produced, not in sporangia) Half of the Ascomycota form lichens (evolved 8 or more times in different orders) but not all lichens are Ascomycotes
  • This begins the first of several photographic reviews of fungal diversity. Enjoy the pictures and try and get a feeling of some of the different forms these fungi take and their roles in the environment.
  • Asexual spores conidia Ecologically important on wood as decomposers and parasites Half the mushrooms form mycorrhizas
  • Bread and wine yeast, the budding yeast, Saccharomyces Easily cultured. For a time, this was the most important organism for studying the molecular genetics of eukaryotes Thus, Saccharomyces is arguably the most important organism known to humans Candida causes diseases of humans, usually experiencing chemical imbalance or immune problems
  • A mold is a rapidly growing, asexually reproducing fungus. The mycelia of these fungi grow as saprobes or parasites on a variety of substrates. Also used in foods (Blue cheese, Tempeh) and in industrial production of drugs Early in life, a mold, a term that applies properly only to the asexual stage, produces asexual spores. Later, the same fungus may reproduce sexually, producing zygosporangia, ascocarps, or basidiocarps Some molds go through a “fake sex” process

Intro to fungi_presentation - fall 2008 Intro to fungi_presentation - fall 2008 Presentation Transcript

  • Kingdom Fungi
    • The characteristics of fungi
    • The evolution of the fungi
    • Fungal classification
    • Fungal life cycles
  • The Characteristics of Fungi
    • Body form
      • unicellular
      • filamentous (tube-like strands called hypha (singular) or hyphae (plural)
      • mycelium = aggregate of hyphae
      • sclerotium = hardened mass of mycelium that generally serves as an overwintering stage.
      • multicellular, such as mycelial cords, rhizomorphs, and fruit bodies (mushrooms)
  • mycelium fruiting bodies both are composed of hyphae
  • The Characteristics of Fungi
    • Heterotrophy - 'other food'
      • Saprophytes or saprobes - feed on dead tissues or organic waste (decomposers)
      • Symbionts - mutually beneficial relationship between a fungus and another organism
      • Parasites - feeding on living tissue of a host. 
        • Parasites that cause disease are called pathogens.
  • Heterotrophic by Absorption
    • Fungi get carbon from organic sources
    • Hyphal tips release enzymes
    • Enzymatic breakdown of substrate
    • Products diffuse back into hyphae
    Enzymes Enzymatic breakdown Products Product diffuses back into hypha and is used Nucleus hangs back and “directs”
  • Hyphae
    • Tubular
    • Hard wall of chitin
    • Crosswalls may form compartments ( ± cells)
    • Multinucleate
    • Grow at tips
  • Hyphal growth
    • Hyphae grow from their tips
    • Mycelium = extensive, feeding web of hyphae
    • Mycelia are the ecologically active bodies of fungi
    This wall is rigid Only the tip wall is plastic and stretches
  • Modifications of hyphae
  • Fungi as Saprobes and Decomposers
  • Fungi as Symbionts (Mutualism)
  • Mycorrhizae
    • “ Fungus roots”
    • Mutualism between:
      • Fungus (nutrient & water uptake for plant)
      • Plant (carbohydrate for fungus)
    • Several kinds
      • Zygomycota – hyphae invade root cells
      • Ascomycota & Basidiomycota – hyphae invade root but don’t penetrate cells
    • Extremely important ecological role of fungi!
  • “ Ecto”mycorrhizae Russula mushroom mycorrhizas on Western Hemlock root Fungal hyphae around root and between cells Mycorrhiza cross sections
  • Lichens
    • “ Mutualism” between
      • Fungus – structure
      • Alga or cyanobacterium – provides food
    • Three main types of lichens:
      • Crustose lichens form flat crusty plates. 
      • Foliose lichens are leafy in appearance, although lobed or branched structures are not true leaves.
      • Fruticose lichens are even more finely branched and may hang down like beards from branches or grow up from the ground like tiny shrubs.
  • Lichen internal structure Lobaria
    • Lichens are nature’s biological monitors of pollution and air quality
      • Thalli act like sponges
      • Some species more sensitive to pollution
      • Which species are present can indicate air quality
      • Most resistant species can also be analyzed for pollutants, including bioaccumulation of heavy metals and radioactive isotopes
  • Fungi as Parasites & Pathogens
  • Fungi are Spore-ific!!!
    • Spores - asexual (product of mitosis) or sexual (product of meiosis) in origin.
    • Purpose of Spores
      • Allows the fungus to move to new food source.
      • Resistant stage - allows fungus to survive periods of adversity.
      • Means of introducing new genetic combinations into a population
  • Reproduce by spores
    • Spores are reproductive cells
      • Sexual (meiotic in origin)
      • Asexual (mitotic in origin)
    • Formed:
      • Directly on hyphae
      • Inside sporangia
      • Fruiting bodies
    Amanita fruiting body Pilobolus sporangia Penicillium hyphae with conidia
  • Hyphal growth from spore
    • Mycelia have a huge surface area
    mycelium germinating spore
  • The Characteristics of Fungi
    • Fungus is often hidden from view. It grows through its food source (substratum), excretes extracellular digestive enzymes, and absorbs dissolved food.
    • Indeterminate clonal growth.
    • Vegetative phase of fungus is generally sedentary.
  • The Characteristics of Fungi
    • Cell wall present, composed of cellulose and/or chitin.
    • Food storage - generally in the form of lipids and glycogen.
    • Eukaryotes - true nucleus and other organelles present.
    • All fungi require water and oxygen (no obligate anaerobes).
    • Fungi grow in almost every habitat imaginable, as long as there is some type of organic matter present and the environment is not too extreme.
    • Diverse group, number of described species is somewhere between 69,000 to 100,000 (estimated 1.5 million species total).
  • Generalized Life Cycle of a Fungus
  • Evolution of the fungi
  • Classification & Phylogeny motile spores zygosporangia asci basidia
  • Chytridiomycota – “chytrids”
    • Simple fungi
    • Produce motile spores - zoospores
    • Mostly saprobes and parasites in aquatic habitats
    • Could just as well be Protists
    Chytridium growing on spores Chytriomyces growing on pine pollen
  • Zygomycota – “zygote fungi”
    • Sexual Reproduction - zygosporangia
    • Asexual reprod. – common (sporangia – bags of asexual spores)
    • Hyphae have no cross walls
    • Grow rapidly
    • Decomposers, pathogens, and some form mycorrhizal associations with plants
    Rhizopus on strawberries Rhinocerebral zygomycosis
  • Life cycle of Rhizopus Asexual sporangium with spores inside Sexual zygsporangium with one zygospore
  • Ascomycota – “sac fungi”
    • Sexual Reproduction – asci (sing. = ascus)
    • Asex. Reprod. – common
    • Cup fungi, morels, truffles
    • Important plant parasites & saprobes
    • Yeast - Saccharomyces
    • Decomposers, pathogens, and found in most lichens
    A cluster of asci with spores inside
  • Sac fungi diversity
  • Basidiomycota – “club fungi”
    • Sexual Reproduction – basidia
    • Asexual reprod – not so common
    • Long-lived dikaryotic mycelia
    • Rusts & smuts –plant parasites
    • Mushrooms, polypores, puffballs, boletes, bird’s nest fungi
    • Enzymes decompose wood, leaves, and other organic materials
    • Decomposers, pathogens, and some form mycorrhizal associations with plants
    SEM of basidia and spores
  • Mushroom Life Cycle Nuclear fusion in basidium Meiosis Hyphal fusion of haploid mycelia haploid mycelium young basidia - the only diploid cells mycelium and fruiting body are dikaryotic N 2N N+N
  • Bioluminescence in Mycena
  • Some fungi have more than one scientific name – Why?
    • Teleomorph : the sexual reproductive stage (morph), typically a fruiting body (e.g., Morchella esculenta , Agaricus brunescens ).
    • Anamorph : an asexual reproductive stage (morph), often mold-like (e.g. Aspergillus flavus , Fusarium solani ). When a single fungus produces multiple morphologically distinct anamorphs, they are called synanamorphs .
    • Holomorph : the whole fungus, including all anamorphs and the teleomorph.
  • Deuteromycota – Form Phylum “Imperfect Fungi”
    • Fungi that seldom or never reproduce sexually.
    • Asexual reproduction by vegetative growth and production of asexual spores common.
  • Yeasts
    • Single celled fungi
    • Adapted to liquids
      • Plant saps
      • Water films
      • Moist animal tissues
    Candida Saccharomyces
  • Molds
    • Rapidly growth
    • Asexual spores
    • Many human importances
      • Food spoilage
      • Food products
      • Antibiotics, etc.
    Noble Rot - Botrytis
  • HUMAN-FUNGUS INTERACTIONS
    • Beneficial Effects of Fungi
      • Decomposition - nutrient and carbon recycling.
      • Biosynthetic factories. Can be used to produce drugs, antibiotics, alcohol, acids, food (e.g., fermented products, mushrooms).
      • Model organisms for biochemical and genetic studies.
    • Harmful Effects of Fungi
      • Destruction of food, lumber, paper, and cloth.
      • Animal and human diseases, including allergies.
      • Toxins produced by poisonous mushrooms and within food (e.g., grain, cheese, etc.).
      • Plant diseases.