Intro to Fungi Presentation - Fall 2008

7/15/2019 Intro to Fungi Presentation - Fall 2008

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Kingdom Fungi

The characteristics

of fungi The evolution of

the fungi

Fungalclassification

Fungal life cycles


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The Characteristics of Fungi Body form

* unicellular* filamentous (tube-like

strands called hypha(singular) or hyphae(plural)

* mycelium = aggregateof hyphae

* sclerotium = hardenedmass of mycelium thatgenerally serves as an

overwintering stage.* multicellular, such as

mycelial cords,rhizomorphs, and fruit

bodies (mushrooms)


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mycelium

fruiting bodies

both arecomposed

of hyphae


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The Characteristics of Fungi

Heterotrophy - 'other food'* Saprophytes or saprobes - feed on dead

tissues or organic waste (decomposers)

* Symbionts - mutually beneficialrelationship between a fungus andanother organism

* Parasites - feeding on living tissue of a

host.

Parasites that cause disease are calledpathogens.


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Heterotrophic by Absorption

Fungi get carbon from organic sources Hyphal tips release enzymes

Enzymatic breakdown of substrate

Products diffuse back into hyphae

Product diffuses back

into hypha and is used

Nucleus hangs back

and directs


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Hyphae

Tubular

Hard wall of chitin

Crosswalls mayform compartments

( cells)

Multinucleate

Grow at tips


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Hyphal growth

Hyphae grow from their tips Mycelium = extensive, feeding web of hyphae

Mycelia are the ecologically active bodies offungi

This wall is rigid Only the tip wall is plastic and stretches


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Modifications of hyphae


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Fungi as Saprobes andDecomposers


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Fungi as Symbionts (Mutualism)


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Mycorrhizae

Fungus roots Mutualism between:* Fungus (nutrient & water uptake for plant)

* Plant (carbohydrate for fungus)

Several kinds* Zygomycotahyphae invade root cells

* Ascomycota & Basidiomycotahyphae invade root but

dont penetrate cells

Extremely important ecological role of fungi!


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Ectomycorrhizae

Russulamushroom

mycorrhizas on

Western

Hemlock root

Fungal hyphae

around root and

between cells

Mycorrhiza cross sections


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Lichens

Mutualism between* Fungusstructure* Alga or cyanobacterium

provides food

Three main types of lichens:* Crustose lichens form flat

crusty plates.

* Foliose lichens are leafy inappearance, although lobed or

branched structures are not true

leaves.* Fruticose lichens are even more

finely branched and may hangdown like beards from branchesor grow up from the ground liketiny shrubs.


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Lichen internal structure

Lobaria

Lichens are natures 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


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Fungi as Parasites & Pathogens


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Fungi are Spore-ific!!!

Spores - asexual (product ofmitosis) or sexual (product ofmeiosis) in origin.

Purpose of Spores

* Allows the fungus to moveto new food source.

* Resistant stage - allowsfungus to survive periods ofadversity.

* Means of introducing newgenetic combinations into a

population


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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


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Hyphal growth from spore

mycelium

germinating

spore

Mycelia have a huge surface area


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Fungus is often hidden from view. It growsthrough its food source (substratum),

excretes extracellular digestive enzymes,and absorbs dissolved food.

Indeterminate clonal growth.

Vegetative phase of fungus is generallysedentary.


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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 isnot too extreme.

Diverse group, number of described species is somewherebetween 69,000 to 100,000 (estimated 1.5 million species total).


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Generalized Life Cycle of a Fungus


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Evolution of the fungi


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Classification

& Phylogeny

motile spores

zygosporangia

ascibasidia


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Chytridiomycotachytrids 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


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Zygomycotazygote fungi

Sexual Reproduction -zygosporangia

Asexual reprod.common

(sporangiabags of asexualspores)

Hyphae have no cross walls Grow rapidly

Decomposers, pathogens, andsome form mycorrhizalassociations with plants

Rhizopus on strawberries

Rhinocerebral zygomycosis


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Life cycle ofRhizopus

Asexual sporangium

with spores inside

Sexual zygsporangium

with one zygospore


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Ascomycotasac fungi

Sexual Reproductionasci(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


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Sac fungi diversity


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Basidiomycotaclub fungi

Sexual Reproductionbasidia Asexual reprodnot socommon

Long-lived dikaryotic mycelia Rusts & smutsplant parasites Mushrooms, polypores,

puffballs, boletes, birds nestfungi

Enzymes decompose wood,leaves, and other organic

materials Decomposers, pathogens, and

some form mycorrhizalassociations with plants SEM of basidia and spores


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Mushroom

Life Cycle

Nuclear

fusion in

basidium

Meiosis

Hyphal fusion

of haploid

myceliahaploid

mycelium

young basidia - the

only diploid cells

mycelium and fruiting

body are dikaryotic

N 2N N+N


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Bioluminescence in Mycena


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Some fungi have more than

one scientific name Why? Teleomorph: the sexual reproductive stage

(morph), typically a fruiting body (e.g.,Morchellaesculenta,Agaricus brunescens).

Anamorph: an asexual reproductive stage(morph), often mold-like (e.g.Aspergillus flavus,

Fusarium solani). When a single fungus producesmultiple morphologically distinct anamorphs, they

are called synanamorphs.

Holomorph: the whole fungus, including allanamorphs and the teleomorph.


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Deuteromycota Form Phylum

Imperfect Fungi Fungi that seldom or never reproduce

sexually.

Asexual reproduction by vegetative growthand production of asexual spores common.


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Yeasts

Single celled fungi

Adapted to liquids* Plant saps

* Water films* Moist animal tissues

CandidaSaccharomyces


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Molds Rapidly growth Asexual spores Many human importances

* Food spoilage

* Food products

* Antibiotics, etc.

Noble Rot -Botrytis


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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.

Intro to Fungi Presentation - Fall 2008

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