Fungi Chapter 31

Fungi

Fungi

Fungi

Fungi More closely related to animals than plants Unicellular Most are multi-cellular Tropics to tundra Aquatics to terrestrial Airborne spores Yeast in breads & beer

Fungi Decomposers Recycle nutrients Help roots of plants absorb nutrients Disease causing (plants and animals) Treatment difficult

Body structure Hyphae Tiny filaments Composed of cytoplasm Surrounded by plasma membrane & cell wall Cell wall made of chitin Septa Cross-walls that separate cells of hyphae

Hyphae

Cell wall Cell wall Nuclei Pore Septum Nuclei (a) Septate hypha Fig. 31-3 Cell wall Cell wall Nuclei Pore Septum Nuclei Figure 31.3 Two forms of hyphae (a) Septate hypha (b) Coenocytic hypha

Body structure Mycelium: Mass of connected hyphae Surrounds & infiltrates material Maximizes contact with material Grows rapidly Grows underground so not visible

Figure 31.19 A fairy ring

Reproduction Each cell can have one or more nuclei Monokaryotic: One nuclei Dikaryotic: Two haploid nuclei that function independently

Reproduction Dikaryotic hyphae Heterokaryotic: Nuclei that are from two genetically distinct individuals Homokaryotic: Nuclei are genetically similar

Reproduction Sexually Asexually Spores are produced either way Spread by wind or on insects Suitable environment give rise to new fungal mycelium

Reproduction Sexual reproduction 2 compatible mating types fuse Usually 2 haploid fuse to form diploid Some fungi remain 1n + 1n and not 2n +/- length of time

Reproduction Plasmogamy: Fusion of cytoplasm of mycelia Karyogamy: Fusion of nuclei Zygotes Meiosis Spore formation

Reproduction Asexually Molds Produce haploid spores by mitosis Yeasts Buds

Haploid (n) Heterokaryotic stage Heterokaryotic (unfused nuclei from Fig. 31-5-3 Key Haploid (n) Heterokaryotic stage Heterokaryotic (unfused nuclei from different parents) PLASMOGAMY (fusion of cytoplasm) Diploid (2n) KARYOGAMY (fusion of nuclei) Spore-producing structures Zygote SEXUAL REPRODUCTION Spores ASEXUAL REPRODUCTION Mycelium Figure 31.5 Generalized life cycle of fungi MEIOSIS GERMINATION GERMINATION Spores

Fungi Heterotrophs Secrete hydrolytic enzymes (exoenzymes) Absorb nutrients(organic molecules)

Nutrients Digest wood (cellulose) Absorb the glucose Lignin (found in wood) Decomposer of living or dead organisms Yield carbon, nitrogen and phosphorus

Nutrients Obtain nutrients from tiny roundworms called nematodes Paralyze Penetrate Absorb nutrients from body Nitrogen source

Metabolic pathways Anaerobic fermentation Wines & cheeses Soy sauce Antibiotics & steroids Yeasts (single cell fungi) Bioremediation Using organisms to break up a toxin

Symbiosis Lichens Fungus & photosynthetic partner (algae) Mutualism some are parasitic Hyphae penetrate cell walls of algae Obtain nutrients from the algae Protects the algae from too much sun

Symbiosis Lichens first to invade a harsh environment Colored - pigments -protect the algae from the sun Pigments are used as natural dyes

Lichen

A foliose (leaflike) lichen A fruticose (shrublike) lichen Figure 31.22 Variation in lichen growth forms Crustose (encrusting) lichens

Mycorrhizae Tree (plant) roots with fungi Fungi function as an extension of roots Plants absorb more nutrients, such as Zn, P, Cu Fungi gets organic materials from the plant

Mycorrhizae 1. Arbuscular: Fungal hyphae penetrate the trees roots Form coils around roots More common 2. Ectomycorrhizae: Hyphae do not penetrate the roots Helps trees grow in infertile areas

Endophytes Fungus lives inside the plant Intercellular spaces Help defend plant against herbivores Symbiotic relationship between fungi & ruminant animals Fungi helps digest the cellulose

Parasitic Mycosis Fungal infection Ringworm Athlete’s foot Candida albicans

Parasitic Aspergillus Produces toxin harmful to humans. Pneumocystis Causes a rare pneumonia in AIDS patients Chytridomycosis Fungal infection that harms amphibians Other fungal infections harm plants Chestnut trees, corn

Distinguishing Features Figure 31.UN07 Fungal Phylum Distinguishing Features Chytridiomycota (chytrids) Flagellated spores Zygomycota (zygomycetes) Resistant zygosporangium as sexual stage Glomeromycota (arbuscular mycorrhizal fungi) Arbuscular mycorrhizae formed with plants Ascomycota (ascomycetes) Sexual spores (ascospores) borne internally in sacs called asci; vast numbers of asexual spores (conidia) produced Figure 31.UN07 Summary of key concepts: fungi lineages Basidiomycota (basidiomycetes) Elaborate fruiting body (basidiocarp) containing many basidia that produce sexual spores (basidiospores)

Fungi Mycologists: scientists that study fungus Five groups 1. Chytrids 2. Zygomycetes 3. Glomeromycetes 4. Ascomycetes 5. Basidiomycetes

1. Chytridiomycota (chytrids) Aquatic fungi Flagellated spores called zoospores Diverged earliest Chitin in the cell walls

2. Zygomycota Bread molds Fruit molds Zygosporangium: Contains one or more diploid nuclei Forms a hard covering Good growth conditions Undergoes meiosis then mitosis Releases spores

Zygomycota Key Haploid (n) Heterokaryotic (n + n) Diploid (2n) Mating PLASMOGAMY Mating type (+) Gametangia with haploid nuclei Mating type (–) 100 µm Young zygosporangium (heterokaryotic) Rhizopus growing on bread SEXUAL REPRODUCTION Dispersal and germination Zygosporangium Sporangia KARYOGAMY Spores Diploid nuclei Sporangium ASEXUAL REPRODUCTION MEIOSIS Dispersal and germination 50 µm Mycelium

BREAD MOLD

Fig. 31-6 2.5 µm Figure 31.6 Penicillium, a mold commonly encountered as a decomposer of food

3. Glomeromycetes Arbuscular mycorrhizae Hyphae with plant roots Very few species

4. Ascomycetes Sac fungi Marine, freshwater & terrestrial Yeast Asci: sac like structure containing sexual spores Ascocarps: contain asci Fruiting bodies Microscopic or macroscopic

Key Ascomycota Conidia; mating type (–) Haploid spores (conidia) Haploid (n) Dikaryotic (n + n) Diploid (2n) Dispersal Germination Mating type (+) ASEXUAL REPRODUCTION Hypha PLASMOGAMY Ascus (dikaryotic) Conidiophore Mycelia Dikaryotic hyphae Mycelium Germination SEXUAL REPRODUCTION KARYOGAMY Dispersal Diploid nucleus (zygote) Asci Eight ascospores Ascocarp Four haploid nuclei MEIOSIS

YEAST

Morchella esculenta Tuber melanosporum Figure 31.15 Figure 31.15 Ascomycetes (sac fungi) Morchella esculenta Tuber melanosporum

5. Blasidiomycetes Mushrooms, shelf fungi, puff balls Blasidium (Latin means “little pedestal”) Long-lived dikaryotic mycelium Leads to more genetic re-combinations Blasidiocarps (mushroom) Produced sexually Fruiting bodies Wood decomposers

Blasidiomycetes Dikaryotic mycelium Haploid mycelia Mating type (–) PLASMOGAMY Mating type (–) Mating type (+) Gills lined with basidia Haploid mycelia SEXUAL REPRODUCTION Basidiocarp (n+n) Dispersal and germination Basidiospores (n) Basidium with four basidiospores Basidia (n+n) Basidium Basidium containing four haploid nuclei KARYOGAMY MEIOSIS Key Haploid (n) Dikaryotic (n +n) Diploid nuclei 1 µm Basidiospore Diploid (2n)

Maiden veil fungus Figure 31.17c Figure 31.17c Basidiomycetes (club fungi) (part 3: maiden veil fungus) Maiden veil fungus