Kingdom FungiKingdom Fungi

Chapter 26Chapter 26

Learning Objective 1Learning Objective 1

• What are the distinguishing characteristics What are the distinguishing characteristics of kingdom Fungi?of kingdom Fungi?

FungiFungi

• Eukaryotic heterotrophsEukaryotic heterotrophs

• Secrete digestive enzymes onto foodSecrete digestive enzymes onto food• then absorb predigested foodthen absorb predigested food

• Cell walls with Cell walls with chitinchitin

KEY CONCEPTSKEY CONCEPTS

• Fungi are eukaryotic heterotrophs that Fungi are eukaryotic heterotrophs that absorb nutrients from their surroundingsabsorb nutrients from their surroundings

Learning Objective 2Learning Objective 2

• What is the body plan of a fungus?What is the body plan of a fungus?

Fungi StructuresFungi Structures

• Fungi includeFungi include• unicellular unicellular yeastyeast • filamentous, multicellular filamentous, multicellular mold mold

• Most multicellular fungiMost multicellular fungi• have long, threadlike filaments (have long, threadlike filaments (hyphaehyphae)) • branch and form a tangled mass (branch and form a tangled mass (myceliummycelium))

Insert “Mycelium”Insert “Mycelium”

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HyphaeHyphae

• In most fungiIn most fungi• perforated perforated septasepta (cross walls) divide hyphae (cross walls) divide hyphae

into individual cellsinto individual cells

• In some fungiIn some fungi• zygomycetes and glomeromyceteszygomycetes and glomeromycetes• hyphae are hyphae are coenocytic coenocytic ((form elongated, form elongated,

multinuclear cell)multinuclear cell)

Fungus Body PlanFungus Body Plan

Fig. 26-1 (a-b), p. 557

Hyphae

25 µm

Fig. 26-1 (c-e), p. 557

KEY CONCEPTSKEY CONCEPTS

• A fungus may be a unicellular yeast or a A fungus may be a unicellular yeast or a filamentous, multicellular mold consisting filamentous, multicellular mold consisting of long, branched hyphae that form a of long, branched hyphae that form a myceliummycelium

Learning Objective 3Learning Objective 3

• What is the life cycle of a typical fungus, What is the life cycle of a typical fungus, including sexual and asexual including sexual and asexual reproduction?reproduction?

ReproductionReproduction

• Most fungi reproduce sexually and Most fungi reproduce sexually and asexually by asexually by sporesspores

• SporesSpores • produced on aerial hyphae produced on aerial hyphae • land in suitable spot and germinateland in suitable spot and germinate

Germination of a SporeGermination of a Spore

Fig. 26-2, p. 557

Spore

Hypha

Mycelium

Asexual ReproductionAsexual Reproduction

Fig. 26-3a, p. 558

Bud development

Fig. 26-3b, p. 558

PlasmogamyPlasmogamy

• Fungi of two different mating types meet, Fungi of two different mating types meet, hyphae fusehyphae fuse

• cytoplasm fusescytoplasm fuses• nuclei remain separate nuclei remain separate

• Fungi enter Fungi enter dikaryoticdikaryotic ( (n n + + nn) stage) stage• each new cell has one nucleus of each typeeach new cell has one nucleus of each type

KaryogamyKaryogamy

• Fusion of nucleiFusion of nuclei• takes place in hyphal tiptakes place in hyphal tip• results in diploid (2results in diploid (2nn) ) zygote nucleuszygote nucleus

Genetic DivisionsGenetic Divisions

• MeiosisMeiosis • produces 4 different haploid (produces 4 different haploid (nn) nuclei) nuclei• each nucleus becomes part of a spore each nucleus becomes part of a spore

• Mitosis Mitosis • forms new mycelia when spores germinate forms new mycelia when spores germinate

Asexual SporesAsexual Spores

• Can be produced by mitosis Can be produced by mitosis • genetically similargenetically similar

• When these spores germinateWhen these spores germinate• they also develop into myceliathey also develop into mycelia

Fungal Life CyclesFungal Life Cycles

Fig. 26-4, p. 559

Large numbers of haploid (n) spores are produced by mitosis.

Spore germinates and forms mycelium by mitosis.Asexual

reproduction

1Spores germinate and form mycelia by mitosis.

Mycelia

Mycelia of two different mating types fuse at their tips, and plasmogamy (fusion of cytoplasm) occurs.

2

6Spores are released. Spores

Sexual reproduction

Haploid stage (n)

Dikaryotic stage (n + n)5

Meiosis results in four genetically different haploid ( n ) nuclei. Spores develop around nuclei.

Diploid stage (2n) 3

Zygote nucleus (2n)

Dikaryotic (n + n) mycelium develops.

Dikaryotic mycelium

4 Karyogamy (fusion of nuclei) occurs, forming a diploid (2 n ) zygote nucleus.

7 8

Meiosis Karyogamy

Plasmogamy

KEY CONCEPTSKEY CONCEPTS

• Most fungi reproduce both asexually and Most fungi reproduce both asexually and sexually by means of sporessexually by means of spores

Learning Objective 4Learning Objective 4

• Support the hypothesis that fungi are Support the hypothesis that fungi are opisthokontsopisthokonts, more closely related to , more closely related to animals than to plantsanimals than to plants

Flagellate CellsFlagellate Cells

• Animals and fungi have flagellate cellsAnimals and fungi have flagellate cells• Example: chytrid gametes and spores Example: chytrid gametes and spores

• Flagellate cells propel themselvesFlagellate cells propel themselves• with single posterior flagellumwith single posterior flagellum

Platelike CristaePlatelike Cristae

• Like animal cells, fungal cells have Like animal cells, fungal cells have platelike cristae in their mitochondriaplatelike cristae in their mitochondria

OpisthokontsOpisthokonts

• Fungi are Fungi are opisthokontsopisthokonts• along with animals and choanoflagellatesalong with animals and choanoflagellates• based on chemical and structural characters based on chemical and structural characters

Fungal EvolutionFungal Evolution

Fig. 26-5, p. 560

Ch

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Evolution of ascospores

Evolution of basidiospores

Evolution of dikaryotic stage

Loss of flagellum

Common flagellate ancestor

Learning Objective 5Learning Objective 5

• Support the hypothesis that Support the hypothesis that chytridschytrids may may have been the earliest fungal group to have been the earliest fungal group to evolve from the most recent common evolve from the most recent common ancestor of fungiancestor of fungi

Chytrids (Chytridiomycetes)Chytrids (Chytridiomycetes)

• Produce Produce flagellate cellsflagellate cells during life cycle during life cycle • no other fungi have flagella no other fungi have flagella

• Probably earliest fungi to evolve from Probably earliest fungi to evolve from flagellate protistflagellate protist

• common ancestor of all fungi common ancestor of all fungi

ChytridChytrid

Fig. 26-6, p. 561

5 µm

Learning Objective 6Learning Objective 6

• List distinguishing characteristics, describe List distinguishing characteristics, describe a typical life cycle, and give examples of a typical life cycle, and give examples of each of these fungal groups: each of these fungal groups:

• chytridiomyceteschytridiomycetes• zygomyceteszygomycetes• glomeromycetes glomeromycetes • ascomycetes ascomycetes • basidiomycetesbasidiomycetes

Chytrids 1Chytrids 1

• Reproduce both asexually and sexually Reproduce both asexually and sexually

• Gametes and zoospores are flagellateGametes and zoospores are flagellate

• AllomycesAllomyces• part of life is multicellular part of life is multicellular haploidhaploid thallusthallus • part is multicellular part is multicellular diploiddiploid thallusthallus

Chytrids 2Chytrids 2

• HaploidHaploid thallus produces 2 types of thallus produces 2 types of flagellate gametes that fuse flagellate gametes that fuse

• Both plasmogamy and karyogamy occurBoth plasmogamy and karyogamy occur• producing flagellate zygoteproducing flagellate zygote

Chytrids 3Chytrids 3

• DiploidDiploid thallus bears zoosporangia thallus bears zoosporangia• produce diploid produce diploid zoosporeszoospores,, resting sporangia resting sporangia• in which haploid zoospores form by meiosis in which haploid zoospores form by meiosis

• Haploid zoospores form new haploid thalliHaploid zoospores form new haploid thalli

Chytrid Chytrid Life CycleLife Cycle

Fig. 26-7a, p. 562

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Common flagellate ancestor

Fig. 26-7b, p. 562

Mature haploid thallus

Sporangium

2

Haploid thallus produces two types of gametes by mitosis.

Haploid zoospore grows into haploid thallus.

Gamete type A

Haploid zoospore

Gamete type B

Haploid zoospores are produced by meiosis.

SEXUAL REPRODUCTION

Resting sporangium

HAPLOID (n) GENERATION

DIPLOID (2n) GENERATION

Gametes fuse and their nuclei fuse, producing flagellate zygote.3

MeiosisPlasmogamy and karyogamy

5Meiosis occurs in resting sporangia.

Resting sporangium

Motile zygote

Zoosporangium

4 Zygote germinates and develops into diploid thallus.

ASEXUAL REPRODUCTION

(by mitosis)

Zoosporangia produce flagellate diploid zoospores by mitosis. Zoospores give rise to new diploid thalli.

7

Diploid zoospore

6

1

ZygomycetesZygomycetes 11

• Rhizopus Rhizopus (black bread mold)(black bread mold)• forms forms haploidhaploid thallus thallus• produces asexual spores and sexual sporesproduces asexual spores and sexual spores

• Asexual spores germinateAsexual spores germinate• form new thalliform new thalli

ZygomycetesZygomycetes 22

• In sexual reproductionIn sexual reproduction• hyphae of 2 different haploid mating types hyphae of 2 different haploid mating types

form form gametangiagametangia

• PlasmogamyPlasmogamy occurs occurs• as as gametangiagametangia fuse fuse

Zygomycetes 3Zygomycetes 3

• KaryogamyKaryogamy occurs occurs• diploid zygotediploid zygote forms forms• from which from which zygosporezygospore develops develops

• Meiosis Meiosis • produces recombinant haploid produces recombinant haploid zygosporeszygospores

Zygomycetes 4Zygomycetes 4

• When When zygosporeszygospores germinate germinate• each hypha develops a each hypha develops a sporangiumsporangium at its tip at its tip

• Spores are releasedSpores are released• develop into new hyphaedevelop into new hyphae

Zygomycete Zygomycete Life CycleLife Cycle

Fig. 26-9a, p. 564

Ch

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Common flagellate ancestor

Fig. 26-9b, p. 564

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MicrosporidiaMicrosporidia

• MicrosporidiaMicrosporidia (now zygomycetes) (now zygomycetes)• are opportunistic pathogensare opportunistic pathogens• penetrate and infect animal cells with long, penetrate and infect animal cells with long,

threadlike threadlike polar tubespolar tubes

Infection by MicrosporidiumInfection by Microsporidium

Fig. 26-10, p. 565

Microsporidian cell

Polar tube

Host cell

1 Spore of microsporidium has coiled polar tube.

Spore ejects its polar tube and penetrates host cell.

Infective cytoplasm is injected into host cell.

2 3

Fig. 26-10, p. 565

Host cell

2. Spore ejects its polar tube and penetrates host cell.

3. Infective cytoplasm is injected into host cell.

Microsporidian cell

Polar tube

1. Spore of microsporidium has coiled polar tube.

Stepped Art

GlomeromycetesGlomeromycetes 11

• Phylum GlomeromycotaPhylum Glomeromycota• symbionts that form intracellular associations symbionts that form intracellular associations

((mycorrhizaemycorrhizae) with plant roots ) with plant roots

• Endomycorrhizal fungiEndomycorrhizal fungi • extend hyphae into root cells extend hyphae into root cells

GlomeromycetesGlomeromycetes 22

• Arbuscular mycorrhizaeArbuscular mycorrhizae • most common endomycorrhizaemost common endomycorrhizae• hyphae inside root cells form branched, tree-hyphae inside root cells form branched, tree-

shaped structures (shaped structures (arbusculesarbuscules))

• GlomeromycetesGlomeromycetes• have coenocytic hyphaehave coenocytic hyphae• reproduce asexually with large, multinucleate reproduce asexually with large, multinucleate

spores (spores (blastosporesblastospores))

Arbuscular MycorrhizaeArbuscular Mycorrhizae

Fig. 26-11, p. 565

Cells of root cortex Root epidermis

VesicleSoil

Root hair

ArbusculeSpore

Cortex cell

Hyphae of fungus

AscomycetesAscomycetes 11

• Produce asexual spores (Produce asexual spores (conidiaconidia) )

• Produce sexual spores (Produce sexual spores (ascosporesascospores) in ) in asci asci

• Asci line a fruiting body (Asci line a fruiting body (ascocarpascocarp))

• ConidiaConidia

• AscocarpAscocarp

• AsciAsci

AscomycetesAscomycetes 22

• Haploid mycelia of opposite mating types Haploid mycelia of opposite mating types produce septate hyphaeproduce septate hyphae

• Plasmogamy occurs, nuclei exchanged Plasmogamy occurs, nuclei exchanged

• Dikaryotic Dikaryotic n +n + n n stage occursstage occurs• hyphae form, produce asci and ascocarphyphae form, produce asci and ascocarp

Ascomycetes 3Ascomycetes 3

• Karyogamy occursKaryogamy occurs• followed by meiosisfollowed by meiosis

• Recombinant nuclei divide by mitosisRecombinant nuclei divide by mitosis• produce 8 haploid nuclei that develop into produce 8 haploid nuclei that develop into

ascosporesascospores

• When ascospores germinateWhen ascospores germinate• can form new myceliacan form new mycelia

AscomycetesAscomycetes 44

• Ascomycetes includeAscomycetes include• yeastsyeasts• cup fungi cup fungi • morels morels • truffles truffles • pink, brown, and blue-green molds pink, brown, and blue-green molds

• Some ascomycetes form mycorrhizaeSome ascomycetes form mycorrhizae• others form lichensothers form lichens

Ascomycete Ascomycete Life CycleLife Cycle

Fig. 26-13a, p. 567

Ch

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Common flagellate ancestor

Fig. 26-13b, p. 567

ConidiaIn asexual reproduction, hyphae produce haploid conidia that can develop into new mycelia.

Germinating conidium

ASEXUAL REPRODUCTION

(by conidia)Conidiophore

Haploid (n)

9When released, ascospores germinate and form new haploid mycelia.

(+) mating type

Haploid mycelia of opposite mating types both produce coenocytic sexual hyphae.

1

(–) mating type

2Plasmogamy occurs as hyphae of the two mating types fuse and nuclei are exchanged.

8Each nucleus becomes incorporated into an ascospore.

Nuclei migratePlasmogamy

SEXUAL REPRODUCTION

Dikaryotic hyphae form and produce asci.

3HAPLOID ( n )

STAGE

Mature ascus has eight haploid ascospores

7Mitosis produces eight haploid nuclei.

DIKARYOTIC STAGE (n + n)

Second meiotic division

DIPLOID (2n)

STAGE

First meiotic division

Nuclei fuse

Developing ascus with n + n nuclei

Hyphae form an ascocarp.4

Zygote

Meiosis 6Meiosis occurs, forming four haploid nuclei.

Karyogamy

Ascocarp

5Karyogamy occurs in each ascus. Two haploid nuclei fuse, forming a diploid zygote nucleus.

Mycelium

10

Insert “Sac fungi”Insert “Sac fungi”

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BasidiomycetesBasidiomycetes 11

• Produce sexual spores (Produce sexual spores (basidiosporesbasidiospores))• on outside of on outside of basidium basidium

• Basidia developBasidia develop• on surface of on surface of gillsgills in mushrooms in mushrooms• a type a type ofof basidiocarp basidiocarp (fruiting body) (fruiting body)

• Hyphae in this phylum have septa Hyphae in this phylum have septa

Basidiomycete Fruiting BodiesBasidiomycete Fruiting Bodies

BasidiomycetesBasidiomycetes 22

• Plasmogamy occursPlasmogamy occurs• fusion of 2 hyphae of different mating types fusion of 2 hyphae of different mating types

• Dikaryotic secondary mycelium forms Dikaryotic secondary mycelium forms

• Basidiocarp developsBasidiocarp develops• basidia form basidia form

BasidiomycetesBasidiomycetes 33

• Karyogamy occursKaryogamy occurs• producing diploid zygote nucleusproducing diploid zygote nucleus

• Meiosis produces 4 haploid nucleiMeiosis produces 4 haploid nuclei• become basidiosporesbecome basidiospores

• When basidiospores germinateWhen basidiospores germinate• form haploid primary myceliaform haploid primary mycelia

Basidium with BasidiosporesBasidium with Basidiospores

Fig. 26-16, p. 570

Basidiospore

Basidium

5 µm

BasidiomycetesBasidiomycetes 44

• Basidiomycetes includeBasidiomycetes include• mushroomsmushrooms• puffballs puffballs • bracket fungi bracket fungi • rustsrusts• smutssmuts

Basidiomycete Life CycleBasidiomycete Life Cycle

Fig. 26-16, p. 570

Basidiospore

Basidium

5 µm

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KEY CONCEPTSKEY CONCEPTS

• According to current hypotheses, fungi According to current hypotheses, fungi evolved from a unicellular, flagellate protist evolved from a unicellular, flagellate protist and diverged into five main groupsand diverged into five main groups

Learning Objective 7Learning Objective 7

• What is the ecological significance of fungi What is the ecological significance of fungi as decomposers?as decomposers?

DecomposersDecomposers

• Most fungi are Most fungi are decomposersdecomposers• break down organic compoundsbreak down organic compounds• dead organisms, leaves, garbage, wastesdead organisms, leaves, garbage, wastes• into simpler nutrients that can be recycledinto simpler nutrients that can be recycled

Learning Objective 8Learning Objective 8

• What is the important ecological role of What is the important ecological role of mycorrhizae?mycorrhizae?

Mycorrhizae 1Mycorrhizae 1

• Mutualistic relationships between fungi Mutualistic relationships between fungi and roots of plantsand roots of plants

• Fungus supplies water and nutrient Fungus supplies water and nutrient minerals to plantminerals to plant

• Plant secretes organic compounds needed Plant secretes organic compounds needed by fungusby fungus

Mycorrhizae 2Mycorrhizae 2

• Glomeromycetes form endomycorrhizal Glomeromycetes form endomycorrhizal associations with rootsassociations with roots

• Ascomycetes and basidiomycetes form Ascomycetes and basidiomycetes form ectomycorrhizaeectomycorrhizae with tree roots with tree roots

• do not penetrate root cellsdo not penetrate root cells

Mycorrhizal AssociationsMycorrhizal Associations

Learning Objective 9Learning Objective 9

• What is the unique nature of a lichen?What is the unique nature of a lichen?

LichenLichen

• Symbiotic combination of fungus and Symbiotic combination of fungus and photoautotroph (alga or cyanobacterium)photoautotroph (alga or cyanobacterium)

• Photoautotroph provides fungus with Photoautotroph provides fungus with organic compounds, shelter, water, organic compounds, shelter, water, minerals minerals

• Lichens have 3 main growth forms: Lichens have 3 main growth forms: crustose, foliose, fruticosecrustose, foliose, fruticose

LichensLichens

Fig. 26-20a, p. 573

Soredia

Surface layer (fungal hyphae)

Fungal hyphae interwoven with photoautotroph

Loosely woven hyphae

Bottom layer (fungal hyphae)

Rock or other surface to which lichen is attached

Fig. 26-20b, p. 573

Fruticose liche (Ramalina)

Crustose lichens (Bacidia, Lecanora)

Foliose lichen (Parmelia)

Insert “Lichens”Insert “Lichens”

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Learning Objective 10Learning Objective 10

• How do fungi impact humans economically?How do fungi impact humans economically?

Useful FungiUseful Fungi

• Fungi are usedFungi are used• as foods (mushrooms, morels, truffles) as foods (mushrooms, morels, truffles) • in production of beer, wine, bread (yeasts)in production of beer, wine, bread (yeasts)• to produce cheeses and soy sauceto produce cheeses and soy sauce• to make citric acid and other industrial to make citric acid and other industrial

chemicalschemicals

Edible AscomycetesEdible Ascomycetes

Learning Objective 11Learning Objective 11

• What is the importance of fungi to biology What is the importance of fungi to biology and medicine?and medicine?

• How do fungi infect plants and humans? How do fungi infect plants and humans?

• Identify at least three fungal plant diseases Identify at least three fungal plant diseases and three fungal animal diseasesand three fungal animal diseases

ResearchResearch

• Fungi are model organisms for molecular Fungi are model organisms for molecular biology and geneticsbiology and genetics

• yeast yeast Saccharomyces cerevisiaeSaccharomyces cerevisiae• other fungi other fungi

• Biological control of insectsBiological control of insects• such as mosquitoes that transmit malariasuch as mosquitoes that transmit malaria

MedicationsMedications

• Fungi are used to make medicationsFungi are used to make medications• penicillin, other antibioticspenicillin, other antibiotics

PathogensPathogens

• Fungi are opportunistic pathogens in Fungi are opportunistic pathogens in humans humans

• ringworm ringworm • athlete’s foot athlete’s foot • candidiasiscandidiasis• histoplasmosishistoplasmosis

ToxinsToxins

• Some fungi produce Some fungi produce mycotoxinsmycotoxins• such as such as aflatoxinsaflatoxins • cause liver damage and cancercause liver damage and cancer

Fungal Plant DiseasesFungal Plant Diseases

• Fungal hyphae infect plants through stomata Fungal hyphae infect plants through stomata • hyphal branches (hyphal branches (haustoriahaustoria) ) penetrate plant cellspenetrate plant cells• obtain nourishment from cytoplasm obtain nourishment from cytoplasm

• IncludeInclude• wheat rustwheat rust• Dutch elm diseaseDutch elm disease• chestnut blightchestnut blight

Fungal Infection of PlantsFungal Infection of Plants

Fig. 26-23, p. 576

Spore Hypha

Epidermis

Stoma

Airspace Leaf

Haustoria

Fungal Plant DiseasesFungal Plant Diseases

KEY CONCEPTSKEY CONCEPTS

• Fungi are of major ecological, economic, Fungi are of major ecological, economic, biological, and medical importancebiological, and medical importance