§    Fungi are classified according to their structure and method of reproduction.

§    The four main groups are:

1.      common mold - Zygomycota

2.      sac fungi - Ascomycota

3.      club fungi - Basidiomycota

4.      imperfecti fungi - Deuteromycota

The Common Molds

§    Phylum Zygomycota are the familiar molds that grow on meat, cheese and bread

§    Their life cycles include a zygospore.

§    A zygospore is a resting spore that contains zygotes formed during the sexual phase of the mold's life cycle.

Structure and Function of Bread Mold

§    Rhizopus stolonifer is black bread mold.

§    There are two different kinds of hyphae on bread mold.

1.      rhizoids - rootlike hyphae that penetrate the bread's surface

►        anchor the fungus to the bread, release digestive enzymes, and absorb digested organic materials

2.      stolons - stemlike hyphae that run along the surface of the bread

►       sporangiophores push up from the stolon and form sporangia at their tips

►       a single sporangia may contain 40,000 spores

Life Cycle of Molds

§    They have both a sexual and asexual phase.

§    The sexual phase begins when hyphae from different mating types fuse and produce gametangium ( gamete­ forming structures)

§    Haploid gametes fuse to produce diploid zygotes.

§    The zygospore develops a thick wall and can remain dormant for a long period of time.

§    The zygospore germinates and a sporangia emerges.

§    The sporangia reproduces asexually by releasing haploid spores produced by meiosis.

The Sac Fungi

§    Phylum Ascomycota is named for the ascus, a reproductive structure that contains spores.

§    It is the largest phylum of the kingdom Fungi.

Life Cycle of Sac Fungi

§    Life cycle includes both asexual and sexual reproduction.

§    In asexual reproduction, tiny spores called conidia, are formed at the tips of conidiophores (specialized hyphae) which can be released under good conditions forming haploid mycelium.

§    Sexual reproduction occurs when haploid hyphae of two different mating types grow close together.

§    They produce a fruiting body where sexual reproduction continues.

§    The ascus forms within the fruiting body that contains two nuclei of different mating types which fuse to form a diploid zygote.

§    Meiosis is follows by mitosis producing ascospores which under the right conditions germinate and grow into haploid mycelium.

Yeasts

§    Yeasts are unicelluar fungi.

§    Humans use them for baking and brewing.

§    The dry granules contain ascospores, which become active in a moist environment.

§    They reproduce asexually by budding (cell division in rapidly growing yeast cells)

§    Yeasts use the process of alcoholic fermentation to obtain energy.

§    The byproducts are carbon dioxide and alcohol.

§    The alcohol in bread dough evaporates during baking and the carbon dioxide make the bread dough rise.

§    These yeasts are called "sugar fungi" due to the fact that they grow in a nutrient rich mixture.

The Club Fungi

§    Phylum Basidiomycota or club fungi gets its name from a specialized reproductive structure that resembles a club.

§    Basidium is the spore-bearing structure.

§    Basidia are found on the gills on the underside of mushroom caps.

Life Cycle of Club Fungi

§    It is the most elaborate life cycle of all the fungi.

§    A basidiospore germinates to produce a haploid primary mycelium, which begins to grow.

§    Mycelia of different mating types fuse to produce a secondary mycelium.

§    Secondary mycelia might grow in the soil for years reaching an enormous size making them the largest organism in the world.

§    When conditions are right, fruiting bodies (mushrooms) push above the ground.

§    The fruiting bodies expand with great speed and may appear overnight.

§    This is caused by cell enlargement NOT cell division.

§    The hyphae enlarge rapidly by taking in water.

§    The mushroom cap exposes hundreds of gills lined with basidia.

§    Basidiospores form at the edge of each basidium and are ready to be scattered.

§    A single mushroom can produce billions of spores, and giant puff balls can produce trillions.

Diversity of Club Fungi

§    Basidiomycetes include:

►       Mushrooms

►       Shelf fungi

►       Puffballs

►       Earthstars

►       Jelly fungi

►       Rusts (plant parasites)

Edible and Inedible Mushrooms

§    Many types of mushrooms have been considered delicacies.

§    Some types are cultivated for food such as the mushrooms on your pizza, portobello mushrooms on your filet and shiitake mushrooms.

§    Wild mushrooms are a different story.

§    The result of eating a poisonous mushroom can be severe illness, or even death.

The Imperfecti Fungi

§    Phylum Deuteromycota is an extremely varies phylum.

§    It is composed of fungi that do not fit into any other phylum because they do not have a sexual phase in their life cycle.

§    They resemble ascomycetes or basidiomycetes or even zygomycetes.

§    The term imperfecti refers to fungi that DO NOT appear to have sexual reproduction.

§    Penicillium is one of the best known imperfecti fungi.

§    This mold grows on fruit and is the source of the antibiotic penicillin.

§    Penicillium reproduces asexually by means of conidia, so it may have evolved from an ascomycete that lost the sexual phase of its life cycle.