Kingdom Fungi

Fungi – What are they?

Diverse group of eukaryotic organisms100,000 to 1,000,000 species

Fungi Characteristics• Kingdom includes

• Molds, mushrooms & yeasts

• Characteristically:• Most are multicellular

(yeasts are unicellular) • Sessile heterotrophs

• secrete enzymes that digest their food outside their bodies then absorb nutrients into their cells

• Have cell walls made of chitin• Use glycogen is energy storage molecule,

not starch• More closely related to animals than plants

(why?)

Fungi Characteristics• Found virtually everywhere

• in soil & water• in light and dark

• Essential decomposers of most ecosystems• Some are parasitic

• mostly on or in plants

• Some symbiotic• many live in very close association with plant roots;

called mycorrhizae, “root fungi”• lichen are symbiotic fungus & algae; species specific

Fungi Characteristics

• Size ranges from unicellular to large• honey mushroom in Oregon has a

mycelial network over 2000 acres in size and is the largest organism on Earth (that is known)

• Most fungi are called obligate aerobes

• must have oxygen to survive

• Some are obligate anaerobes and some can deal with both anaerobic and aerobic conditions.

• ex. yeast – intermediate, Chytridiomycota – obligate anaerobes found in the gut (rumen) of cattle

Fungi Characteristics• Two part “body plan”1. Feeding

• hyphae: thread-like filaments that form a network called mycelium or a thallus (more generic than mycelium)

• lots of surface area to secrete digestive enzymes

• called exoenzymes• small holes in the hyphae septa (the point

where cells join) allow for increased nutrient uptake

2. Reproductive• the mushroom (the “fruiting body”); tightly

packed mycelium; above ground to disperse spores

Fungus reproduction• Reproduction in fungi can be “perfect” or “imperfect”

• perfect fungi can reproduce both asexually and sexually• imperfect fungi can only reproduce asexually• Asexual

• spores produced by mitosis• release of spores dispersed (by wind, water or animals) that can develop into a

multicellular haploid individual• may also occur by fragmentation or budding

conidia fungus producing asexual spores

Fungus reproductionSexual

• 2 haploid mycelia of different mating types (+ and - ) release signaling molecules & grow toward each other & fuse

• cytoplasm fuses but not nuclei; for a while, cells are dikaryotic (!!)

• eventually nuclei fuse forming diploid stage (the “fruiting body”); haploid spores are produced by meiosis

• these spores then form haploid mycelia

Fungi Classification• The Kingdom Fungi is divided in to “divisions” – these equated to phyla

in classification• Based primarily on reproductive strategies

• There are four divisions that reproduce sexually = Perfect Fungi1. Chytridiomycota (chytrids)

• unique due to flagellated zoospores, some have both chitin and cellulose• oldest and simplest true fungi

2. Zygomycota (conjugated fungi)• bread molds, most are saprobes, produce resistant spores (zygospores)

which may remain dormant for long periods of time

Fungi Classification• The Kingdom Fungi is divided in to “divisions” – these equated to phyla

in classification• Based primarily on reproductive strategies

3. Basidiomycota (club fungi)• includes “mushrooms”, shelf fungus, smuts, toadstools• sometimes called gill fungi due to the gill-like structures under the cap

4. Ascomycota (sac fungi)• form an ascus (sac), includes yeasts and some disease causing fungi

(fungal pneumonia)• conidia are the asexual reproductive structures,

and asci are the sexual reproductive structures

• Two divisions that reproduces only asexually = Imperfect Fungi• Deuteromycota – now recognized as the asexual variants of Ascomycota and Basidiomycota• Glomeromycota - all live symbiotically with tree roots, forming arbuscular

mycorrhizae (structures which take in nutrients and provide minerals)

Fungi Uses

Ecological uses• Decomposers

• crucial role in nutrient cycling• May form symbiotic

relationships with plants• plants get water and minerals• fungus gets glucose

• Environmentally Beneficial in mycorestoration

• have the ability to remove toxins from the environment

Human uses• food by themselves & in cheese &

yogurt; yeast in bread & alcoholic drinks

• produce antibiotics• soaps, dyes & food colorings

TED – Six Ways Fungi Can Save the World!

Next Time… Plants!