Kingdom fungi
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Kingdom Fungi. The characteristics of fungi The evolution of the fungi Fungal classification Fungal life cycles Human-Fungus Interactions. The Characteristics of Fungi. Body form unicellular (yeasts) filamentous (tube-like strands called hypha (singular) or hyphae (plural)

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Kingdom Fungi

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Kingdom Fungi

  • The characteristics of fungi

  • The evolution of the fungi

  • Fungal classification

  • Fungal life cycles

  • Human-Fungus Interactions


The Characteristics of Fungi

  • Body form

    • unicellular (yeasts)

    • filamentous (tube-like strands called hypha (singular) or hyphae (plural)

    • mycelium = aggregate of hyphae

    • Some fungi are dimorphic!

      Multicellular

    • sclerotium = hardened mass of mycelium that generally serves as an overwintering stage.

    • multicellular, such as mycelial cords, rhizomorphs, and fruit bodies (mushrooms)


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

Products

Enzymatic breakdown

Nucleus hangs back

and “directs”

Enzymes

Product diffuses back

into hypha and is used


Tubular

Hard wall of chitin

Crosswalls may form compartments (± cells)

Multinucleate

Grow at tips

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


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

Mycorrhiza cross sections

Fungal hyphae around root and between cells


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

  • 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

Lobaria


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

Penicillium hyphae with conidia

Pilobolus sporangia

Amanita fruiting body


Mycelia have a huge surface area

Hyphal growth from spore

germinating

spore

mycelium


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


asci

basidia

zygosporangia

Classification & Phylogeny

motile spores


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”

Rhizopus on strawberries

  • 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

Rhinocerebral zygomycosis


Sexual zygsporangium with one zygospore

Asexual sporangium with spores inside

Life cycle of Rhizopus


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


mycelium and fruiting body are dikaryotic

Mushroom Life Cycle

haploid mycelium

Hyphal fusion of haploid mycelia

N 2N N+N

Meiosis

Nuclear fusion in basidium

young basidia - the only diploid cells


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

Antibiotic activity


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.


Fungi

Classification of fungal diseases (mycoses)

Superficial, cutaneous, subcutaneous

Systemic and opportunistic

Poisoning and allergies

Treatment

Azole drugs, amphotericin B, others


Cutaneous and subcutaneous

Dermatophytes: various genera

Cause skin and nail diseases

Referred to as tinea (worm) because of the ring-like appearance on scalp and skin.

Cause ringworm, jock itch, athlete’s foot, etc.

Limited to outer layer of skin

Sporothrix schenkii

Acquired from soil and plant material

Infects deeper into skin, but not systemic


Systemic Mycoses

Generally acquired by inhalation of spores

Lung infections, may spread beyond into other tissues

Blastomyces (blastomycosis)

Coccidiodes (coccidiomycosis)

Histoplasma (histoplasmosis)

Most common in this area (Ohio and Miss. River valleys)

Soil contaminated with bird or bat droppings

Many people exposed with asymptomatic cases

Many test positive for exposure


Opportunistic infections

Aspergillus (aspergillosis)

Variety of species, very common in soil, plant materials

Serious infections in immunocompromised

Allergies to A. fumigatus

Poisoning from aflatoxin from A. flavus

Candida (candidiasis)- normal microbiota

Cause of vaginal infections, diaper rash, thrush

Capable of infecting any part of the body

Dangerous in cancer patients, HIV infections, etc.


Opportunists-2

Cryptococcus neoformans

Inhalation of spores

Can infect many parts, but has predilection for CNS

Particularly serious in AIDS

Pneumocystis carinii

Very protozoan like, but is a fungus

Most cases associated with AIDS

Serious lung infections: PCP (P. carinii pneumonia)


Fusarium

ATLANTA, Aug. 23 -- Minus a smoking gun, CDC researchers have nonetheless indicted a contact lens solution that was removed from the market earlier this year in the wake of a widespread outbreak of Fusarium keratitis.

Contact lens wearers should not use ReNu with MoistureLoc, made by Bausch & Lomb of Rochester, N.Y., said Douglas Chang, M.D., of the CDC here, and colleagues.

http://www.medpagetoday.com/Ophthalmology/GeneralOphthalmology/tb/3980


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