fungi, structure ,evolution and classification

FUNGI : FUNGI NONVASCULAR, ACHLOROPHYLLUS, HETEROTROPHIC, SPORE BEARING EUCARYOTIC, CHITINOUS CELL WALL, GLYCOGEN AS RESERVE FOOD MYCOLOGY

Kingdom Fungi : Kingdom Fungi The characteristics of fungi The evolution of the fungi Fungal classification Fungal life cycles

Slide 3 : Occur in dark & damp places, few aquatic- Allomyces, Achlya. To date, 100,000 species of fungi have been discovered.  It is thought that  there are over one million  species still  to be found. Achlorophyllous, but other pigments can be seen. Body is mycelium, multicellular ( not yeast), uninucleate or multinucleate. Cell wall is chitinous – fungal cellulose No embronic stage

The Characteristics of Fungi : The Characteristics of Fungi Body form unicellular -yeast 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)

Slide 5 : mycelium fruiting bodies both are composed of hyphae

The Characteristics of Fungi : 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 : 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 : Hyphae Tubular Hard wall of chitin-fungal cellulose Crosswalls may form compartments (± cells) Multinucleate Grow at tips

Hyphal growth : 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 : Modifications of hyphae

Fungi as Saprobes and Decomposers : Fungi as Saprobes and Decomposers

Fungi as Symbionts (Mutualism) : Fungi as Symbionts (Mutualism)

Mycorrhizae : 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 : “Ecto”mycorrhizae Russula mushroom mycorrhizas on Western Hemlock root Fungal hyphae around root and between cells Mycorrhiza cross sections

Lichens400 genera ,15000 species : Lichens400 genera ,15000 species “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 : 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 as Parasites & Pathogens

Fungi are Spore-ific!!! : 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 : 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 Caesar roman emperor was poisoned by wife

Hyphal growth from spore : Hyphal growth from spore mycelium germinating spore Mycelia have a huge surface area

The Characteristics of Fungi : 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 : The Characteristics of Fungi Food storage - generally in the form of lipids and glycogen. Eukaryotes - true nucleus and other organelles present. All fungi require water and oxygen 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.

Generalized Life Cycle of a Fungus : Generalized Life Cycle of a Fungus

Slide 24 : Evolution of the fungi

Slide 25 : Classification & Phylogeny motile spores zygosporangia asci basidia

Chytridiomycota – “chytrids” : 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” : 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

Slide 28 : Life cycle of Rhizopus Asexual sporangium with spores inside Sexual zygsporangium with one zygospore

Ascomycota – “sac fungi” : 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 : Sac fungi diversity

Basidiomycota – “club fungi” : 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 : 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 : Bioluminescence in Mycena

Some fungi have more than one scientific name – Why? : 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” : Deuteromycota – Form Phylum “Imperfect Fungi” Fungi that seldom or never reproduce sexually. Asexual reproduction by vegetative growth and production of asexual spores common.

Yeasts : Yeasts Single celled fungi Adapted to liquids Plant saps Water films Moist animal tissues Candida Saccharomyces

Molds : Molds Rapidly growth Asexual spores Many human importances Food spoilage Food products Antibiotics, etc. Noble Rot - Botrytis

HUMAN-FUNGUS INTERACTIONS : 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.