list distinguishing characteristics, describe a typical

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Fungi

Learning Objectives

• By the end of this unit, a student should be able to…

• List distinguishing characteristics, describe a typical life cycle,

and give examples of each of the following fungal groups:

chytridiomycetes, zygomycetes, glomeromycetes, ascomycetes,

and basidiomycetes

• Describe the body plan of a fungus

• Summarize the ecological significance of fungi as decomposers

• Describe the important ecological role of mycorrhizae

• Characterize the unique nature of a lichen

• Summarize some specific ways that fungi affect humans

economically

• Summarize the importance of fungal diseases to agriculture and

medicine; giving specific examples

Distinguishing characteristics of Fungi

• Eukaryotic heterotrophs

• Secrete digestive enzymes externally, absorb nutrients

• Cell walls contain chitin

• fibrous polysaccharide

• polymer of a N-acetylglucosamine (derivative of glucose)

• also found in exoskeleton of arthropods

Fungal Structure

• Threadlike filaments (hyphae)

• Branch and form a tangled mass (mycelium)

Fungal Structure

• Threadlike filaments (hyphae)

• Branch and form a tangled mass (mycelium)

Fungal Structure

• Hyphae

• Perforated septa

(cross walls) divide

hyphae into individual

cells

• Some are coenocytic

• form elongated,

multinuclear cell

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Fungal Reproduction

• reproduce with Spores

• sexual

• asexual

• produced on aerial hyphae

• produced in a “fruiting

body”

Fungal Reproduction

Giant Puffball (Calvatia gigantea)

• A single ten-inch giant puffball has as many as

7 trillion (7,000,000,000,000) spores.

• If each of those spores grew and yielded a ten-inch

puffball, the combined mass would be 800 times that

of the earth.

• From the Cornell Mushroom Blog, David Landers

Yeast

• Yeasts are a type of single celled fungus

• highly reduced mycelium

• reproduce asexually by budding

Life cycles

• Mitosis

• Meiosis

• Fertilization

Ex: Homo sapiens

Fungal Life cycles

Fungal Life Cycle

n

haploid mycelium

dikaryotic

mycelium

Spores n

n

mitosis

meiosis

n

plasmogamy

n + n

karyogamy

2n

diploid

mycelium

n n

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haploid mycelium

dikaryotic

mycelium

Spores

mitosis

meiosis

plasmogamy

karyogamy

diploid

mycelium

(n)

Fungal Life cycles

asexual cycle of

haploid mycelium

Spores (n)

Fungal Evolution

• Chytridiomycetes

• Zygomycetes

• Glomeromycetes

• Ascomycetes

• Basidiomycetes

Chytrids (Chytridiomycetes)

• Produce flagellate cells

• no other fungi have flagella

• a shared characteristic of the

opisthokonts

• Probably earliest fungi to

evolve from flagellate protist

Chytridium convervae


• “Chytrid” and Chytridiomycosis disease

• Massive amphibian die-off

• mainly in tropics

• Caused by fungus Batrachochytrium dendrobatidis


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Fungal Evolution


• Zygomycetes

• Glomeromycetes

• Ascomycetes

• Basidiomycetes

Zygomycota

• Hyphae are coenocytic

• septa form to separate the hyphae from

reproductive structures

Zygomycota

• Sexual reproduction

• hyphae of 2 different mating types form gametangia

• Plasmogamy occurs as gametangia fuse

• Karyogamy produces zygote (2n)

• zygote develops into zygosporangium

Zygomycota

• Sexual reproduction

• zygosporangium produces zygospores (n)

• zygospores germinate and produce sporangia

• sporangia produce spores (n) which germinate into new

hyphae

Zygomycota Life Cycle

Example:

Rhizopus stolionifer

(black bread mold)

Zygomycota

• Microsporidia

• Small, unicellular opportunistic pathogens that infect

eukaryotic cells

• May be the smallest and simplest eukaryotes

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Zygomycota

• Microsporidia

• Previously classified with yeasts, bacteria, and protista

• Genome studies suggest that microsporidia descended

from a zygomycete ancestor

Fungal Evolution


• Zygomycetes

• Glomeromycetes

• Ascomycetes

• Basidiomycetes

Glomeromycetes (Phylum Glomeromycota)

• Coenocytic hyphae

• reproduce asexually with large, multinucleate

blastospores

• form mycorrhizae

• mutualistic symbiosis with plant roots

Glomeromycetes (Phylum Glomeromycota)

• Mycorrhizae*

• form associations with roots of

trees and herbaceous plants

• specifically, endomycorrhizal

• grow into plant root cells

• called arbuscular

mycorrhizae

• form tree-shaped

structures

* a description of ecology, not phylogeny

–Johnny Appleseed

“Type a quote here.”

Cells of root

cortex Root epidermis

Soil Vesicle

Root hair

Arbuscule Spore

Cortex cell

Hypha of fungus

Mycorrhizal Associations

• Roots supply organic nutrients

• Fungus provides mineral nutrients

Pine w/o mycorrhizae Pine with mycorrhizae

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Fungal Evolution


• Zygomycetes

• Glomeromycetes

• Ascomycetes

• Basidiomycetes

Ascomycetes (Phylum Ascomycota)

• Ascomycetes include

• yeasts

• cup fungi

• morels

• truffles

• pink, brown, and blue-

green molds

Ascomycetes

• Have septate hyphae

• Produce coenocytic sexual hyphae

• Following plasmogamy, dikaryotic (n + n) hyphae

form in an ascocarp* (fruiting body)

Ascocarp -

“fruiting body”

*made of monokaryotic hyphae

Ascomycetes

• Karyogamy occurs at tips of hyphae (asci)

• followed by meiosis and mitosis

• produces 8 haploid nuclei that develop into ascospores

Asci - form

sexual spores in

groups of 8

Ascomycetes (Phylum Ascomycota)

• Asexual reproduction

• involves formation of

colored spores (conidia)

at the tips of specialized

hyphae (conidiophores)

Penicillium conidiophores

–Johnny Appleseed

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Fungal Evolution


• Zygomycetes

• Glomeromycetes

• Ascomycetes

• Basidiomycetes

Basidiomycetes

• Phylum Basidiomycota

• include the largest and

most familiar of the fungi

• mushrooms

• bracket fungi

• puffballs

• rusts

• smuts

Basidiomycetes

• Septate hyphae

• a secondary mycelium

forms after plasmogamy

• dikaryotic hyphae

• compact buttons grow into

mushrooms (fruiting bodies)

called basidiocarps

Basidiomycetes (Phylum Basidiomycota)

• Karyogamy takes place within

young basidia on the gills of the

mushroom

• each basidium produces 4

basidiospores

–Johnny Appleseed

“Type a quote here.”

Basidiospores

released

Plasmogamy

HAPLOID (n)

STAGE

Second meiotic

division DIKARYOTIC

STAGE

(n + n) First meiotic

division DIPLOID (2n)

STAGE

Meiosis Zygote

Karyogamy Gills Basidiocarp

Secondary mycelium

1

2

3

4

5

6

7 • Many basidiomycetes produce “fairy rings” in lawns

and forests

• The circle widens as the fungi grow outward

Basidiomycetes

list distinguishing characteristics, describe a typical

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