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Chap 1 classification of fungi
 

Chap 1 classification of fungi

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  • 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
  • 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.
  • 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.
  • 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
  • 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.

Chap 1 classification of fungi Chap 1 classification of fungi Presentation Transcript

  • MIC 206 MYCOLOGYCLASSIFICATION OF FUNGI
  • Sub-Topic Brief Criteria of the Fungi Kingdom Differences between the Old and Modern Classification Difficulties of Classifying Fungi Introduction, Basic Characteristics and Life Cycles
  • Definitions MYCOLOGISTS MYCOLOGY MYCOSES FUNGUS FUNGI
  • Definitions Mycologists : scientists who study fungi. Mycology : scientific discipline dealing with fungi. Mycoses : diseases caused in animals by fungi.
  • Fungus versus Fungi “Fungus” is used inclusively for a heterogenous group of organisms that have traditionally been studied by mycologists . “Fungi” refers to the organisms in the Kingdom Fungi, the true fungi, also called the “Eumycota”.
  • How many species of fungi exist?- 90,000 species of fungi described- 1,700 new species described each year
  • What is a fungus?A eukaryotic organisms. Fungi are neithera plants, nor animalsA heterotrophic organism devoid ofchlorophyll that obtains its nutrients byabsorption.Heterotrophic by absorption.Reproduced by spores.The primary carbohydrate storageproduct of fungi is glycogen.
  • Most fungi have a thallus composed ofhyphae (sing. hypha) that elongate by tipgrowth.The fungal thallus consists of hyphae; amass of hyphae is a mycelium.
  • The Characteristics of Fungi Structure – hyphae, mycelium, thalus Heterotrophic by Adsorption Reproduced by Spores
  • Kingdom FungiNutritional Type HeterotrophMulticellularity All, except yeasts Unicellular, filamentous,Cellular Arrangement fleshyFood Acquisition Method AbsorptiveCharacteristic Features Sexual and asexual sporesEmbryo Formation None
  • Structure of fungi
  • 1) The Structure - Hyphae Hyphae = tubular units of construction  Tubular  Hard wall of chitin  Cross walls may form compartments (± cells)  Multinucleate  Grow at tips
  • Modifications of hyphae
  • Hyphal growthHyphae grow from their tipsMycelium = extensive, feeding web ofhyphaeMycelia are the ecologically active bodies offungi This wall is rigid Only the tip wall is plastic and stretches
  • Hyphal growth from sporegerminating spore mycelium
  • 2. Heterotrophic by Absorption Fungi get carbon from organic sources Hyphal tips release enzymes Enzymatic breakdown of substrate Products diffuse back into hyphae Nucleus hangs back and “directs” Product diffuses back into hypha and is used
  • 3. Reproduced by spores Spores are reproductive cells Sexual Asexual Formed: Pilobolus sporangia Directly on hyphae Inside sporangia Fruiting bodies Amanita fruiting body Penicillium hyphae
  • OLD AND MODERNCLASSIFICATION OF FUNGI
  • Old Classification Carl Linnaeus (1707-1778) the “Father of Taxonomy” “ Minerals exist; plants exist and live; animals exist, live and sense.” Plants without obvious sexual organs were classified in Class Cryptogamia (lichens, fungi, mosses, ferns) Fungi are primitive plants under this classification of organisms.
  • Old ClassificationThe Five kingdom system (Whittaker, 1969) Eukarya (includes all organism with a nucleus & membrane bound organelles). Plants and Animals are fairly obvious Fungi, are very distinct from the other kingdoms. Kingdom Protista is a “dumping ground” for organisms that don’t fit into the other eukaryotic kingdoms.
  • R. H. Whittaker’s 1969 Classification
  • KINGDOM CHARACTERISTIC EXAMPLE     Monera Prokaryocyte Bacteria ActinomycesProtista Eukaryocyte ProtozoaFungi Eukaryocyte * FungiPlants Eukaryocyte Plants MossAnimals Eukaryocyte * Arthropods Mammals Man
  • Modern Classification At least 7 kingdoms are now recognized (Patterson & Sogin 1992) :  Eubacteria,  Archaebacteria,  Animalia,  Plantae,  Eumycota,  Stramenopila (Chromista),  Protoctista (Protozoa, Protista)
  • Based on molecular evidence: base sequencesfrom ribosomal RNA (Patterson & Sogin 1992)
  • Systems of classifying fungi1) 1860HOGG proposed the term PROTOCTISTA - fungi and neitherPlant or Animal.This kingdom composed mostly of unicellular organisms.The kingdom was later replaced by 2 kingdoms – MYCOTA &MONERA (prokaryotes) and PROTOCTISTA(eukaryotes).2) 1947Microscopes enable study of complex structural characteristics.New classification (WOLF & WOLF, 1947)3) 1969Fungi in its own kingdom by WHITTAKER – FUNGI KINGDOM.
  • Systems of classifying fungi4) 1998Modification by MARGUILIS & SCHWARTZ – used characteristics(structure & function).• MONERA: Prokaryotes – bacteria, actinomycetes, blue-green algae.• PROTOCTISTA: Eukaryotes – protozoa and other unicellular and colonial organisms such as water moulds, slime moulds and slime nets.• FUNGI : Eukaryotes – organisms that lack flagella that develop from spores such as yeast, molds, rusts and mushrooms.• PLANTAE: Eukaryotes – organisms that develop from embryos such as liverworts, mosses and vascular plants.• ANIMALIA: Eukaryotes – organisms that develop from a blastula (hollow ball of cells) such a sponges, worms, arthropods and mammals.
  • Marguilis and Schwartz (1998)Classify the fungi into 3 phyla : Zygomycota, Ascomycota and Basidiomycota.Chytrids (CHYTRIDIOMYCOTA) in the Kingdom Proctista.Deuteromycota with their closest relatives that are the Ascomycota and Basidiomycota.Lichen with the Phylum Ascomycota.
  • Other classificationsMOORE, 1998 (quoted from Pfieffer, M., et al., 2001) states that plants, animals and fungi can be separated based on how they obtain energy.Plants possess chloroplasts as photosynthetic structures used to produce food.Animals possess mitochondria used for internalized digestion.Fungi excrete enzymes into the food source they live within external digestion.
  • Classification using molecularresearch techniquesBALDAUF & PALMER (1993), WAINWRIGHT et al. (1993) and HASEGAWA et al (1993)The above current schemes agree that the three major kingdoms are separated→ thereby confirmed that there are no connection between the fungi-plant kingdom.
  • QuestionFill in the blanks of the systematic of classification1) Kingdom2) Division / Phylum3) ___________4) Order5) ___________6) Tribe7) ___________8) Species Sometimes there are subdivisions and subclasses
  • QuestionFill in the blanks of the systematic of classification1) Kingdom2) Division / Phylum3) Class4) Order5) Family6) Tribe7) Genus8) Species Sometimes there are subdivisions and subclasses
  • Hierarchical ClassificationKingdom Fungi Phylum Basidiomycota Class Basidiomycetes Order Agaricales Family Agaricaceae Genus Agaricus Species: Agaricus campestris L.
  • How are fungi named? To determine the correct name for a taxon, certain steps must be followed, including:  Effective publication  Valid publication • Description or diagnosis in Latin • Clear indication of rank • Designated type
  • Nomenclature Nomenclature: the “allocation of scientific names to the units a systematist considers to merit formal recognition.” (Hawksworth et al., 1995. The Dictionary of the Fungi).  The nomenclature of fungi is governed by the International Code for Botanical Nomenclature, as adopted by the International Botanical Congress.
  • Reasons why it is not easy toclassify fungi Fungi comprise of a broad number of organisms. Fungi have various forms depending on the environment and conditions in which they grow. Many terms being used to describe the morphological structures of fungi.
  • Basic Characteristics andLife Cycles Ascomycota (inc.Deuteromycota) Basidiomycota Zygomycota
  • Ascomycota – “sac fungi” Teleomorphic fungi  Produce sexual and asexual spores Sex. – asci Asex. – common Cup fungi, morels, truffles Important plant parasites & saprobes Yeast - Saccharomyces Septate Most lichens A cluster of asci with spores inside
  • Basidiomycota – “club fungi” Produce basidiospores and sometimes conidiospores Sex – basidia Asex – not so common Long-lived dikaryotic mycelia Rusts & smuts – primitive plant parasites Septate Mushrooms, polypores, puffballs Enzymes decompose wood Mycorrhizas SEM of basidia and spores
  • Zygomycota – “zygote fungi” Conjugation fungi Coenocytic Sex - zygosporangia Asex - common Produce sporangiospores and zygospores Hyphae have no cross walls Grow rapidly Rhizopus, Mucor (opportunistic, systemic Fig 31.6 Rhizopus on mycoses) strawberries Mycorrhizas
  • True Fungi versus Slime MouldsTrue fungi:- those that are hyphal- possess cell walls throughout most of their life cycle- are exclusively absorptive in their nutrition.Slime moulds:- those that do not form hyphae- lack cell walls during the phase that they obtain nutrients and grow- are capable of ingesting nutrients by phagocytosis. So they are more common to Protista although they produce fruiting bodies like fungi.- The most studied of them are the cellular slime moulds and the plasmodial slime moulds or Myxomycetes.
  • QUESTIONThe fungus can never be classified inPlantae or Animalia?EXPLAIN WHY?(Hint ! LOOK AT ITS MOBILITY, REPRODUCTION & NUTRITION)