Fungi

Ch. 22

pp. 482-95

Kingdom Fungi - Characteristics

• Fungi first appeared on earth around 430

million years ago.

• In the past, fungi were grouped with plants

because they shared several common

features:

– Immobile

– Cell wall

– Some appear rooted in the soil (mushrooms)

Characteristics Cont’d

• Key Characteristcs of Fungi:

– Heterotrophic • Energy comes from breaking down organic

material in the environment.

– Multicellular

– Filamentous Bodies • Made of long, slender filaments that are tightly

woven together to form the body of the fungus.

– Cells contain chitin • Tough polysaccharide found in the cell walls of

fungi.

Structures • Hyphae compose the body of the fungi (except

yeast)

– slender filaments

– long string of cells divided by partial walls

allowing cytoplasm to flow freely between

cells

Structure continued • Mycelium is a tangled mass of hyphae

• This complex of hyphae (mycelium) gives

the fungus a high surface- area-to-volume

ratio.

• Can be many meters in length.

How would this benefit the fungus?

ANSWER

– Has the ability to absorb more nutrients from

the environment.

Cell Walls

• Made of chitin

• Chitin is also found in the exoskeleton

of insects

• It is a polysaccharide

– What type of biological macromolecule

is this?

Nutrition

• HETEROTROPHIC

• saprobe: obtains energy by breaking down organic material

• digestive enzymes are secreted by fungi to break down organic material and the compounds are then absorbed for energy

• organic material used by fungi for energy:

– dead leaves, branches, dead animals, waste

– living hosts are parasitized by fungi like ringworm and athletes foot

Ring Worm of the Scalp

Athlete’s foot

RING WORM

Apply antifungal medications to the lesion itself

and 1 inch beyond its border twice daily for a

minimum of two weeks, and at least one week

after it goes away. Keep the infected area clean

and dry. Medications available at the drugstore

include miconazole 2% (with brand names such

as Monistat and Micatin) or clotrimazole 1% (with

brand names such as Lotrimin and Mycelex).

-Ringworm is highly contagious.

-Avoid touching suspicious lesions.

-Maintain proper hygiene by washing your hands

and body frequently

-Avoid contact sports such as wrestling until you

have been treating the lesions for at least 48

hours.

ATHLETES FOOT

Keep the area clean and dry. Buy shoes that are leather or other

breathable material. Powders, especially medicated powders

(such as with miconazole or tolnaftate), can help keep your feet

dry.

Soak feet in a drying solution of aluminum acetate (Burrow's

solution or Domeboro's solution). A homemade remedy of dilute

white vinegar soaks using one part vinegar and roughly four parts

water, once or twice a day as 10-minute foot soaks may aid in

treatment.

Use antifungal creams and washes (miconazole or Lamisil)

Treatment for athlete's foot should generally be continued for four

weeks, or at least one week after all of the skin symptoms have

cleared.

Reproduction

• Can be sexual or asexual

• Occurs through the release of spores from

structures at the tips of hyphae.

• Reproductive Strategies:

– Reproductive structures grow high above the food

source.

– This adaptation allows air currents to carry spores to

a new habitat.

– Spores are very light and can be carried great

distances before falling back to the ground.

Fungus releasing spores

Review: a spore is like a tiny seed

• Light weight, can float long distances

• Can withstand extreme conditions until the

environment is favorable for germination

Asexual Reproduction

• Some may have filaments that break from

the main mycelium and grow into new

individuals

• Some produce spores that disperse,

germinate, divide and produce genetically

identical fungi

– Spores can withstand extreme dryness and

cold to produce new fungi when conditions

permit

Sexual Reproduction

• Fused hyphae form a sexual reproductive

structure

• On this structure, the fungus forms spores

through fusion of two genetically different

nuclei.

• The type of structures produced during

sexual reproduction determine the Phyla

to which a species belongs.

Reproductive Structures

• Based on the structures formed during

sexual reproduction, fungi can be grouped

in 4 phyla:

– Chytridiomycota

– Zygomycota

– Ascomycota

– Basidiomycota

Chytridiomycota

• Most ancient of fungus

• Have motile spores

• Live in water

• Are killing frogs world wide

Carcass of frog killed by a Chytridiomycota

Zygomycetes – Molds

• Species of Rhizopus or bread

molds

• Sexual structures have thick walls

zygosporangia

• Usually live in the soil and feed on

decaying plant and animal matter.

• Other anatomical structures:

– Stolon: mycelia that grow on surface

– Rhizoids: hyphae that anchor the

fungus in the bread

haploid

haploid

haploid

Zygomycetes

• Reproduction:

– Asexual

– Haploid spores are produced in the

zygosporangia.

– When the haploid spores mature, they are

released and carried by the wind to new

locations.

– In the new location they germinate and

grow new mycelia.

– Spores like these cause fungal allergies

Ascomycetes-Sac Fungi

• Examples: – Endothia parasitica

Kills chestnut trees

– Saccharomyces cerevisiae

Baker’s yeast

– Candida albicans Causes thrush

• Sexual Structure: Ascus – Sac-like structure in

which haploid spores are formed.

Yeast asexually reproducing by BUDDING

Oral Thrush, common in infants

Basidiomycetes-Club Fungi

• Examples: Mushrooms, toadstools, puffballs, jelly fungi, and shelf fungi.

• Sexual Structure = basidium – Club-like structure where

spores are produced.

• Asexual reproduction is rare and occurs mainly in rusts and smuts (plant pathogens).

DEATH CAP MUSHROOM

• Toxin blocks production of DNA (why is

this a problem?)

• Causes nausea, kidney and liver failure,

coma and DEATH in 30% of all people

who ingest them.

• Mutualism: type of symbiotic relationship

in which each partner benefits.

• LICHENS

– Fungus (heterotrophic), provides minerals and

other nutrients absorbed from the

environment.

– Algae or Plant (photosynthetic autotroph)

provides the ability to use sunlight to build

carbohydrates.

Fungal

Relationships

Mycorrhizae

• Relationship between fungi and vascular plant roots.

– Hyphae help transfer phosphorus and minerals to the roots of plants.

– The plants provide carbohydrates to the fungus.

– What kind of symbiotic relationship is this?

Parasitic Fungi

• Parasitism:

– A form of symbiosis where one

organsim benefits from the

other species, and usually

causes harm to the host.

• Parasitic fungi compete for

nutrients with the host and

sometimes cause infections:

– Athlete’s Foot

– Yeast Infections

– Histoplasmosis

• Fungal infection of the lungs

• Caused by the fungus

Histoplasma capsulatum

Fungi in your life

• Fungi often grows on food, such as bread

and fruits.

• Yeasts are useful in baking, brewing, and

wine-making.

• Fungi provide the aroma and flavor of some

cheeses.

• Many antibiotics are produced from fungi…

– penicillin

– streptomycin