Kingdom Fungi

 Fungi grow as filaments called hyphae (singular: hypha).  A mass of hyphae is called mycelium  Some fungi have septa (singular: septum), or cross walls, which divide the filament into compartments containing a single nucleus. Cell walls of fungi are made of chitin, a nitrogen- containing polysaccharide

 Fungi are either parasites or saprobes (feed on dead organic material).  They absorb the breakdown products from the action of digestive enzymes that they secrete.

 Many parasitic fungi have hyphae called haustoria that penetrate their host. Fungal haustoria showing penetration of a plant cell by a powdery mildew fungus

 Fungi live their lives predominantly as haploid organisms.  They form temporary diploid structures for sexual reproduction.  They can also reproduce asexually. All of the cells shown in the diagram above are haploid cells. The diploid cells that undergo meiosis are not shown.

 The following stages occur during sexual reproduction:  1. Plasmogamy-the fusing of cells from 2 different fungal strains produce a single cell with nuclei from both (called a dikaryon)  2. Karyogamy is the fusing of 2 haploid nuclei of a dikaryon to form a single diploid nucleus. 3. After growing a fruiting body such as this mushroom, meiosis of the diploid nucleus results in haploid spores.

Plasmogamy Karyogamy

 Fungi reproduce asexually by various means, including:  Fragmentation-the breaking up of hyphae  They can also reproduce asexually by budding or by producing asexual spores. Fragmentation: The above picture shows the hyphae of a fungus called Scytalidium. Each hyphae has formed into individual cells which can separate from each other and grow into new fungus organisms.

 Fungi can reproduce asexually by budding.  In this process, a small hyphal outgrowth is pinched off and forms a new organism.  Yeast reproduces this way most of the time. Yeast budding—the yellow structures are scars where new yeast cells budded off.

 Asexual spores can be:  Sporangiospores— produced in saclike capsules called sporangia that are each borne on a stalk called a sporangiophore.

 The second kind of asexual spores can be:  Conidia—formed at the tips of specialized hyphae  These are not enclosed inside sacs  Hyphae that bear conidia are called conidiophores.

 Zygomycota  Glomeromycota  Ascomycota  Basidiomycota  Deuteromycota  Lichens

 Zygomycota lack septa (cross walls), except when their filaments border reproductive filaments.  Reproduce sexually by fusion of hyphae from different strains.  Haploid zygospores are produced, which germinate into new hyphae.

 Glomeromycota lack septa (cross walls) and do not produce zygospores.  They are a small group of fungi that occur only in mutualistic associations with the roots of plants.  This fungus-root relationships are called mycorrhizae. In this relationship, the plant provides carbohydrate to the fungus and the fungus helps the roots absorb nutrients, especially phosphorus. These fungi do not cause any diseases to the plant, they only help it.

 Ascomycota have septa (cross walls) and reproduce sexually by producing haploid ascospores.  The ascomycetes include yeasts, powdery mildews, and truffles.  More about their reproduction on the next slide! Truffles are wild mushrooms that grow underground. They are used in gourmet cooking and are VERY expensive ($800-$6000/oz.). They are found by specially trained pigs or dogs.

 After plasmogamy of hyphae from unlike strains, a dikaryotic hypha produces more filaments by mitosis. (A)  Karyogamy and meiosis subsequently occur in terminal hyphal cells producing four haploid cells. (B) These four cells divide by mitosis to produce 8 haploid ascospores in a sac called an ascus. (C) A B C

 A study of crossing over—AP Lab 3 A study of crossing over—AP Lab 3  k12.wi.us:8100/~jdick son/AP_Biology/ex7 _5/index.htm k12.wi.us:8100/~jdick son/AP_Biology/ex7 _5/index.htm

 Basidiomycota have septa (cross walls) and reproduce sexually by producing haploid basidiospores.  Plasmogamy between two unlike hyphae is followed by mitosis and the growth of dikaryotic hyphae to form a fruiting body called a basiocarp.  A mushroom is a basiocarp.

 Deuteromycota are also called imperfect fungi.  This is an artificial group comprising of fungi for which no sexual reproductive cycle has been observed.  Penicillium (which produces penicillin) is a deuteromycete. Penicillin was discovered by Alexander Fleming. He noticed that a certain type of mold inhibited bacterial growth in one of his petri dishes.

 Lichens are mutualistic associations between fungi and algae.  The algae, which is usually a chlorophyta or cyanobacteria, provides sugar from photosynthesis.  The fungus (most often an Ascomycete) provides water and protection from the environment. Some fungi produce pigments that shield the algae from UV radiation or excess light, or toxic substances that discourage algae consumption by grazers.

 Video: /watch?v=XuKjBIBBAL8 /watch?v=XuKjBIBBAL8 ube.com/watch?v =22OOs0dGg4A ube.com/watch?v =22OOs0dGg4A The Cordyceps fungus attacks insects, infiltrating their bodies and brains, eventually killing them. Before they die, however, they climb to the highest plant in their ecosystem so the spores are distributed to a large area.