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 neither a plants, nor animals A heterotrophic organism devoid of chlorophyll that obtains its nutrients by absorption. Heterotrophic by absorption. Reproduced by spores. The primary carbohydrate storage product of fungi is glycogen.
Most fungi have a thallus composed of hyphae (sing. hypha) that elongate by tip growth. The fungal thallus consists of hyphae; a mass of hyphae is a mycelium.
The Characteristics of Fungi Structure – hyphae, mycelium, thalus Heterotrophic by Adsorption Reproduced by Spores
Kingdom Fungi Nutritional Type Heterotroph Multicellularity All, except yeasts Cellular Arrangement Unicellular, filamentous, fleshy Food Acquisition Method Absorptive Characteristic Features Sexual and asexual spores Embryo 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 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
Hyphal growth from spore germinating 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 MODERN CLASSIFICATIO N 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 Classification The 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.
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 sequences from ribosomal RNA (Patterson & Sogin 1992)
Systems of classifying fungi 1) 1860 HOGG proposed the term PROTOCTISTA - fungi and neither Plant or Animal. This kingdom composed mostly of unicellular organisms. The kingdom was later replaced by 2 kingdoms – MYCOTA & MONERA (prokaryotes) and PROTOCTISTA(eukaryotes). 2) 1947 Microscopes enable study of complex structural characteristics. New classification (WOLF & WOLF, 1947) 3) 1969 Fungi in its own kingdom by WHITTAKER – FUNGI KINGDOM.
Systems of classifying fungi 4) 1998 Modification 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 classifications MOORE, 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 molecular research techniques BALDAUF & 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.
Question Fill in the blanks of the systematic of classification 1) Kingdom 2) Division / Phylum 3) ___________ 4) Order 5) ___________ 6) Tribe 7) ___________ 8) Species Sometimes there are subdivisions and subclasses
Question Fill in the blanks of the systematic of classification 1) Kingdom 2) Division / Phylum 3) Class 4) Order 5) Family 6) Tribe 7) Genus 8) Species Sometimes there are subdivisions and subclasses
Hierarchical Classification Kingdom 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 to classify 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 and Life 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 Moulds True 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.
QUESTION The fungus can never be classified in Plantae or Animalia? EXPLAIN WHY? (Hint ! LOOK AT ITS MOBILITY, REPRODUCTION & NUTRITION)