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Overview: Mighty Mushrooms

Overview: Mighty Mushrooms. Fungi are diverse and widespread They are essential for the well-being of most terrestrial ecosystems because they break down organic material and recycle vital nutrients. Fungi are heterotrophs that feed by absorption.

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Overview: Mighty Mushrooms

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  1. Overview: Mighty Mushrooms • Fungi are diverse and widespread • They are essential for the well-being of most terrestrial ecosystems because they break down organic material and recycle vital nutrients

  2. Fungi are heterotrophs that feed by absorption • Despite their diversity, fungi share key traits, most importantly the way in which they derive nutrition • Fungi are heterotrophs but do not ingest their food • They secrete exoenzymes that break down complex molecules, and then they absorb the smaller compounds • Fungi exhibit diverse lifestyles: Decomposers, parasites and mutualistic symbionts

  3. Body Structure • The morphology of multicellular fungi enhances their ability to absorb nutrients • Fungi consist of mycelia, networks of branched hyphae adapted for absorption • Most fungi have cell walls made of chitin • Some fungi have hyphae divided into cells by septa, with pores allowing cell-to-cell movement • Coenocytic fungi lack septa • Some unique fungi have specialized hyphae that allow them to penetrate the tissues of their host

  4. Reproductive structure Hyphae Spore-producing structures 20 µm Mycelium

  5. Cell wall Cell wall Nuclei Pore Septum Nuclei Septate hypha Coenocytic hypha

  6. Hyphae 25 µm Nematode Hyphae adapted for trapping and killing prey Plant cell wall Fungal hypha Plant cell Plant cell plasma membrane Haustorium Haustoria

  7. Mycorrhizae are mutually beneficial relationships between fungi and plant roots • Ectomycorrhizal fungi form sheaths of hyphae over a root and also grow into the extracellular spaces of the root cortex • Endomycorrhizal fungi extend hyphae through the cell walls of root cells and into tubes formed by invagination of the root cell membrane

  8. Fungi produce spores through sexual or asexual life cycles • Fungi propagate themselves by producing vast numbers of spores, either sexually or asexually

  9. Key Heterokaryotic stage Haploid (n) 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 MEIOSIS GERMINATION GERMINATION Spore-producing structures Spores

  10. Sexual Reproduction • Plasomogamy is the union of two parent mycelia • In many fungi, the haploid nuclei from each parent do not fuse right away; they coexist in the mycelium, called a heterokaryon • In some fungi, the haploid nuclei pair off two to a cell; such a mycelium is said to be dikaryotic

  11. Hours, days, or even centuries may pass before the occurrence of karyogamy, nuclear fusion • During karyogamy, the haploid nuclei fuse, producing diploid cells • The diploid phase is short-lived and undergoes meiosis, producing haploid spores

  12. Asexual Reproduction • In addition to sexual reproduction, many fungi can reproduce asexually • Many of these species grow as mold, sometimes on fruit, bread, and other foods

  13. 2.5 µm

  14. Other fungi that can reproduce asexually are yeasts, which inhabit moist environments • Instead of producing spores, yeasts reproduce asexually by simple cell division

  15. 10 m Parent cell Bud

  16. Arbuscular mycorrhizal fungi Sac fungi Club fungi Zygote fungi Chytrids Chytridiomycota Glomeromycota Basidiomycota Zygomycota Ascomycota

  17. Zygomycetes • The zygomycetes (phylum Zygomycota) exhibit great diversity of life histories • They include fast-growing molds, parasites, and commensal symbionts • The zygomycetes are named for their sexually produced zygosporangia • The life cycle of black bread mold (Rhizopus stolonifer) is fairly typical of the phylum

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

  19. Zygosporangia, which are resistant to freezing and drying, can survive unfavorable conditions • Some zygomycetes, such as Pilobolus, can actually “aim” their sporangia toward conditions associated with good food sources

  20. 0.5 mm

  21. Ascomycetes • Ascomycetes (phylum Ascomycota) live in marine, freshwater, and terrestrial habitats • The phylum is defined by production of sexual spores in saclike asci, usually contained in fruiting bodies called ascocarps • Ascomycetes vary in size and complexity, from unicellular yeasts to elaborate cup fungi and morels

  22. The cup-shaped ascocarps (fruiting bodies) of Aleuria aurantia give this species its common name: orange peel fungus. The edible ascocarp of Morchella esculenta, the succulent morel is often found under trees in orchards. 10 µm Neurospora crassa feeds as a mold on bread and other food (SEM). Tuber melanosporum is a truffle, an ascocarp that grows underground and emits strong odors. These ascocarps have been dug up and the middle one sliced open.

  23. Ascomycetes reproduce asexually by enormous numbers of asexual spores called conidia • Conidia are not formed inside sporangia; they are produced asexually at the tips of specialized hyphae called conidiophores

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

  25. Basidiomycetes • Basidomycetes (phylum Basidiomycota) include mushrooms and shelf fungi • The phylum is defined by a clublike structure called a basidium, a transient diploid stage in the life cycle

  26. Maiden veil fungus (Dictyphora), a fungus with an odor like rotting meat Fly agaric (Amanita muscoria), a common species in conifer forests in the northern hemisphere Puffballs emitting spores Shelf fungi, important decomposers of wood

  27. In response to environmental stimuli, the mycelium reproduces sexually by producing elaborate fruiting bodies call basidiocarps • Mushrooms are examples of basidiocarps • The numerous basidia in a basidiocarp are sources of sexual spores called basidiospores

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

  29. Fungi have a powerful impact onecosystems and human welfare Decomposers • Fungi are efficient decomposers • They perform essential recycling of chemical elements between the living and nonliving world Symbionts • Fungi form symbiotic relationships with plants, algae, and animals • All of these relationships have profound ecological effects

  30. Mycorrhizae • Mycorrhizae are enormously important in natural ecosystems and agriculture • They increase plant productivity RESULTS RESULTS

  31. Fungus-Animal Symbiosis • Some fungi share their digestive services with animals • These fungi help break down plant material in the guts of cows and other grazing mammals • Many species of ants and termites use the digestive power of fungi by raising them in “farms”

  32. Lichens • Lichens are a symbiotic association of millions of photosynthetic microorganisms held in a mass of fungal hyphae • The fungal component of a lichen is most often an ascomycete • Algae or cyanobacteria occupy an inner layer below the lichen surface

  33. A fruticose (shrub-like) lichen A foliose (leaf-like) lichen Crustose (crust-like) lichens

  34. Ascocarp of fungus Soredia Fungal hyphae Algal layer Algal cell Fungal hyphae 10 µm

  35. Pathogens • About 30% of known fungal species are parasites, mostly on or in plants • Animals are much less susceptible to parasitic fungi than are plants • The general term for a fungal infection in animals is mycosis

  36. Corn smut on corn Tar spot fungus of sycamore leaves Ergots on rye

  37. Practical Uses of Fungi • Humans eat many fungi and use others to make cheeses, alcoholic beverages, and bread • Genetic research on fungi is leading to applications in biotechnology • Antibiotics produced by fungi treat bacterial infections

  38. Staphylococcus Penicillium Zone of inhibited growth

  39. Animations and Videos • Life Cycles of Zygomycetes, Ascomycetes and Basidomycetes • The Ascomycetes • Ascus Animation • Basidium Animation • The Basidiomycetes • Conidia Animation • Life Cycle of Cycle of a Zygomycetes • Life Cycle of a Bread Mold

  40. Animations and Videos • Life Cycle of a Slime Mold • Chapter Quiz Questions – 1 • Chapter Quiz Questions - 2

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