Chapter 21

Kingdom Fungi

20-1 Learning Targets

• What are the characteristics of Fungi?

• What is the internal structure of a fungus?

• How do fungi reproduce?

Fungi Characteristics

• VERY different from plants:

– No roots, stems or leaves – Have no chlorophyll

• Eukaryotic heterotrophs with cell walls

– Cell wall made of CHITIN – Digest food outside of body and THEN absorb it through cell wall • Some absorb nutrients from decaying matter – Called Detritus Feeders – Example of Detritus feeder: Club fungi/mushrooms • Some live as parasites – Example of Parasitic feeder: Ring worm • Some live in symbiotic relationship that benefits both sides

More Characteristics

• All fungi are multicellular (except yeast) • Multicellular fungi are made of tiny filaments called hyphae

– Hyphae tangle together in a thick mass to form the mycelium or fungal body – Mycelium lies below the ground and the fruiting body or reproductive structure is above ground (the “mushroom”)

Hyphae

Cell wall Nuclei Cytoplasm Cytoplasm

Hyphae With Cross Walls

Cross wall Nuclei Cell wall

Hyphae Without Cross Walls

Kingdom Fungi

Hyphae Fruiting Body Mycelium

Fairy Rings

• Some mycelia can live for many years

– Over time, the nutrients at the center of the mycelium become depleted – New mushrooms only sprout at the edges of the mycelium, causing a ring • Called a “FAIRY RING”

Reproduction in Fungi

• Fungi reproduce both sexually and asexually • Fungi are classified according to their structure and method of reproduction • General Groups:

– Common Molds – Sac Fungi – Club Fungi – Imperfect Fungi

Zygomycota includes Common molds

Fungi

are divided into the phyla Ascomycota includes Sac fungi Basidiomycota Deuteromycota includes Club fungi includes Imperfect fungi

20-2 Learning Targets

• What are the characteristics of the four major phyla of Fungus?

Common Molds

• Phylum Zygomycota: called zygomycetes

– Common molds that grow on meat, cheese and bread

• Best Known Zygomycete:

– Rhizopus stolonifer (black bread mold)

• Structure

– The mycelium is the cottony white mass of a bread mold.

– The black balls at the top of the filaments are called SPORANGIA or spore cases.

– This fungus sends out filaments across the top of the bread.

– These filaments secrete digestive enzymes and absorb the digested food externally

Rhizopus

Rhizopus

Reproduction

• Rhizopus reproduces asexually by spore formation

– Each spore has a nucleus and is surrounded by a black wall.

– The outer wall of the sporangium is very delicate and easily torn.

• When torn, the exposed spores are quickly carried away by air • The spores then grow and reproduce on a moist surface.

• The mold also reproduces sexually

– We will not learn this process in detail, you just need to know that it is possible!

Rhizopus Life Cycle

Zygospore (2N) Sporangium

FERTILIZATION

Gametangia

MEIOSIS

Zygospore (2N) Sporangium Spores (N) Spores (N) Sporangiophore Stolons

Asexual Reproduction

Rhizoids + Mating type (N) - Mating type (N)

Sexual Reproduction

Diploid Haploid

Sac Fungi

• Phylum Ascomycota: called Ascomycetes

– Named for the ASCUS, their reproductive structure that contains spores – Largest Phylum of Kingdom Fungi – Some ascomycetes such as cup fungi are visible on the ground, others like yeasts are microscopic – EXAMPLES: Morels, Truffles

YEAST

• Yeast are unicellular fungi used by humans for baking and brewing

– Cause bread to rise by producing CO 2 in fermentation

• They can reproduce sexually and form ascospores • They reproduce asexually by budding

– A bulge appears on the cell wall.

– The nucleus splits and moves into the bulge.

– The bulge grows but may remain attached to the mother cell.

– Chains grow and may eventually break.

Yeast Budding

Club Fungi

• Phylum Basidiomycota: called basidiomycetes or club fungi

– Gets name from reproductive structure that resembles a club (called a basidium) – The cap of the basidiomycete (like a mushroom) is made of tightly packed hyphae • The lower side of the cap is made of GILLS – Gills are thin blades of tissue lined with cells that produce spores – Spores are scattered to produce more mushrooms – Examples: Mushrooms, Shelf Fungi, Puffballs, Earthstars, jelly fungi

Basidiomycete Life Cycle

Button Secondary mycelium (N + N) HYPHAE FUSE Cap Fruiting body (N + N) Primary mycelium (N) - Mating type (N) Gills lined with basidia Gills Stalk Base Zygote (2N) Basidia (N + N) FERTILIZATION Haploid Diploid + Mating type (N) Basidiospores (N) MEIOSIS

Basidiomycete Pictures

Puffballs Shelf Fungi:

form next to dead/decaying trees

Stinkhorns

• Stinkhorns are a family of basidiomycetes

– They produce a foul-scented mushroom

• Their method of reproduction is different than most mushrooms, which use the air to spread their spores

– Stinkhorns produce a sticky spore mass on their tip which has an odor that attracts flies – The flies land on the stinkhorn and collect the spores on their legs and carry it to other locations.

Stinkhorn

Just a Warning

• Many types of fungi are delicacies and are cultivated for food (Portabellas are yummy!) • Many wild mushrooms are also edible, BUT many are POISONOUS

– Many species of edible mushrooms look identical to poisonous mushrooms

• Moral of the Story: Don’t pick and eat mushrooms unless you know what you are doing!

Imperfect Fungi

• Phylum Deuteromycota: called deuteromycetes or imperfect fungi • Extremely diverse group– basically the misfit fungi

– Fungi go here when researchers have not found a sexual phase in their life cycles

• EXAMPLES:

Penicillium

, Ringworm, Athlete’s Foot

Penicillium

•

Penicillium

is mold that grows on fruit and is source of antibiotic UP CLOSE!!!

Mold on an orange

Importance of Fungi

• FOOD SOURCE

– Mushrooms – Morels – a delicacy – Yeast – used in baking and fermentation – Truffles – very expensive delicacy

• MEDICINES:

– Penicillin – from Penicillium – Cyclosporin – anti-rejection drug

Morels and Truffles

Importance of Fungi

• DISEASES

– Ringworm-from deuteromycete – Athlete’s foot fungus-from deuteromycete – Thrush – Candida albicans – Yeast infections • Using antibiotics increases risk of yeast infections because the medicines kill helpful, symbiotic bacteria in humans.

– Dutch elm disease – Chestnut blight

Ringworm

Importance of Fungi

• IN NATURE:

– Decompose and recycle detritus.

– Lichens – symbiotic relationship between a fungus and algae (see p. 540) • Usually neither can grow on their own • Can grow in harsh environments due to relationship (fungus gets water, minerals, and other carries out photosynthesis) – Mycorrhizae –symbiotic relationships between plants and fungi • Fungus helps obtain more nutrients by increasing surface area (plant also provides nutrients) • About 90% of plants have a miycorrhizal relationship – Fungi kill nematodes – a roundworm that attacks crops

Lichens