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What is the biggest organism in this Oregonian forest? Hint, it is pictured The honey mushroom fungus Fun-gi vids • • • • pig decomposition time-lapse fungus time-lapse growing mold time-lapse parasitic fungi time-lapse LECTURE PRESENTATIONS For CAMPBELL BIOLOGY, NINTH EDITION Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson Chapter 31 Fungi Lectures by Erin Barley Kathleen Fitzpatrick © 2011 Pearson Education, Inc. Concept 31.1: Fungi are heterotrophs that feed by absorption • Fungi are heterotrophs and absorb nutrients from outside of their body • Fungi use enzymes to break down a large variety of complex molecules into smaller organic compounds • Fungi exhibit diverse lifestyles – Decomposers – rabbit decomposing – Parasites – previously shown, with new bonus mushroom and slime mold time-lapse – Mutualists © 2011 Pearson Education, Inc. Animation: Fungal Reproduction and Nutrition Right-click slide / select “Play” © 2011 Pearson Education, Inc. Anatomy basics • Fungi consist of mycelia, networks of branched hyphae adapted for absorption • A mycelium’s structure maximizes its surface area-to-volume ratio • Fungal cell walls contain chitin © 2011 Pearson Education, Inc. Figure 31.2 Reproductive structure Hyphae Spore-producing structures 60 m Mycelium TWO FORMS OF HYPHAE Nuclei Cell wall Cell wall Pore Septum (a) Septate hypha Nuclei (b) Coenocytic hypha 1 pinch of soil can contain 1 km of hyphae How much hyphae did she eat? Nematode Some unique fungi have specialized hyphae called haustoria that allow them to penetrate the tissues of their host Hyphae 25 m (a) Hyphae adapted for trapping and killing prey Fungal hypha Plant cell wall Plant cell Haustorium (b) Haustoria Plant cell plasma membrane • Mycorrhizae are mutually beneficial relationships between fungi and plant roots, which most vascular plants have – Ectomycorrhizal fungi form sheaths of hyphae over a root and also grow into the extracellular spaces of the root cortex – Arbuscular mycorrhizal fungi extend hyphae through the cell walls of root cells and into tubes formed by invagination of the root cell membrane • Which is pictured ? • Which is pictured on the previous slide? © 2011 Pearson Education, Inc. Concept 31.2: Fungi produce spores through sexual or asexual life cycles • Fungi propagate themselves by producing vast numbers of spores, either sexually or asexually, or both © 2011 Pearson Education, Inc. Fungi life cycle paths can be funky Key Haploid (n) Heterokaryotic Diploid (2n) Spore-producing structures Spores Mycelium ASEXUAL REPRODUCTION GERMINATION Fungi life cycle paths can be funky Key Haploid (n) PLASMOGAMY Heterokaryotic Heterokaryotic stage Diploid (2n) Spore-producing structures Spores Mycelium ASEXUAL REPRODUCTION GERMINATION KARYOGAMY SEXUAL REPRODUCTION Zygote Fungi life cycle paths can be funky Key Haploid (n) PLASMOGAMY, Heterokaryotic based on pheromone compatibility Heterokaryotic stage Diploid (2n) Spore-producing structures KARYOGAMY Spores Mycelium ASEXUAL REPRODUCTION GERMINATION SEXUAL REPRODUCTION Zygote GERMINATION MEIOSIS Spores © 2011 Pearson Education, Inc. Asexual Reproduction • In addition to sexual reproduction, many fungi can reproduce asexually • Molds produce haploid spores by mitosis and form visible mycelia © 2011 Pearson Education, Inc. Figure 31.7 CHECK-IN Q • Yeast are unicellular and reproduce by budding. Then what makes them fungi? 10 m Parent cell Bud Concept 31.3: The ancestor of fungi was an aquatic, single-celled, flagellated protist • DNA evidence suggests that – Fungi are most closely related to unicellular nucleariids – Animals are most closely related to unicellular choanoflagellates • Based on this, did fungi and animals split before or after the emergence of multicellularity? © 2011 Pearson Education, Inc. The Move to Land • If fungi are heterotrophic, how does it make sense that they were among the first land colonizers? © 2011 Pearson Education, Inc. The Move to Land • If fungi are eukaryotic, how does it make sense that they were among the first land colonizers? © 2011 Pearson Education, Inc. Concept 31.4: Fungi have radiated into a diverse set of lineages • Molecular analyses have helped clarify evolutionary relationships among fungal groups, although areas of uncertainty remain © 2011 Pearson Education, Inc. Figure 31.11 Hyphae 25 m Fungal hypha 25 m Chytrids (1,000 species) Zygomycetes (1,000 species) Glomeromycetes (160 species) Ascomycetes (65,000 species) Basidiomycetes (30,000 species) Chytrids • Chytrids (phylum Chytridiomycota) are found in freshwater and terrestrial habitats • They can be decomposers, parasites, or mutualists • Molecular evidence supports the hypothesis that chytrids diverged early in fungal evolution • Chytrids are unique among fungi in having flagellated spores, called zoospores © 2011 Pearson Education, Inc. Video: Allomyces Zoospore Release © 2011 Pearson Education, Inc. Video: Phlyctochytrium Zoospore Release © 2011 Pearson Education, Inc. Zygomycetes • The zygomycetes (phylum Zygomycota) exhibit great diversity of life histories • They include fast-growing molds, parasites, and commensal symbionts • The life cycle of black bread mold (Rhizopus stolonifer) is fairly typical of the phylum • Its hyphae are coenocytic • Asexual sporangia produce haploid spores © 2011 Pearson Education, Inc. Figure 31.UN02 Chytrids Zygomycetes Glomeromycetes Ascomycetes Basidiomycetes Figure 31.13 PLASMOGAMY Mating type () Mating type () Gametangia with haploid nuclei 100 m Rhizopus growing on bread Young zygosporangium (heterokaryotic) SEXUAL REPRODUCTION Dispersal and germination Zygosporangium KARYOGAMY Flagellum Sporangia Sporangium ASEXUAL REPRODUCTION Diploid nuclei MEIOSIS Key Dispersal and germination 50 m Mycelium Haploid (n) Heterokaryotic (n n) Diploid (2n) • The zygomycetes are named for their sexually produced zygosporangia • Zygosporangia are the site of karyogamy and then meiosis • 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 © 2011 Pearson Education, Inc. Figure 31.14 0.5 mm Pilobolus aiming its sporangia toward light as that is where edible vegitation would be growing (grass). Grass is eaten, spores spread in feces. Glomeromycetes • The glomeromycetes (phylum Glomeromycota) were once considered zygomycetes • They are now classified in a separate clade • Glomeromycetes form arbuscular mycorrhizae © 2011 Pearson Education, Inc. Figure 31.UN03 Chytrids Zygomycetes Glomeromycetes Ascomycetes Basidiomycetes Figure 31.15 2.5 m Ascomycetes • Ascomycetes (phylum Ascomycota) live in marine, freshwater, and terrestrial habitats • Ascomycetes produce sexual spores in saclike asci contained in fruiting bodies called ascocarps • Ascomycetes are commonly called sac fungi • Ascomycetes vary in size and complexity from unicellular yeasts to elaborate cup fungi and morels © 2011 Pearson Education, Inc. Figure 31.UN04 Chytrids Zygomycetes Glomeromycetes Ascomycetes Basidiomycetes Figure 31.16 Morchella esculenta, the tasty morel Tuber melanosporum, a truffle • Ascomycetes include plant pathogens, decomposers, and symbionts • 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 • Neurospora crassa, a bread mold, is a model organism with a well-studied genome © 2011 Pearson Education, Inc. Figure 31.17 Conidia; mating type () Key Dispersal Germination Haploid (n) Dikaryotic (n n) Diploid (2n) Mating type () ASEXUAL REPRODUCTION Hypha PLASMOGAMY Ascus (dikaryotic) Conidiophore Mycelia Dikaryotic hyphae Mycelium Germination Dispersal Asci Ascocarp SEXUAL REPRODUCTION Eight ascospores KARYOGAMY Diploid nucleus (zygote) Four haploid nuclei MEIOSIS Basidiomycetes • Basidomycetes (phylum Basidiomycota) include mushrooms, puffballs, and shelf fungi, mycorrhizae, and plant parasites • The phylum is defined by a clublike structure called a basidium, a transient diploid stage in the life cycle • The basidiomycetes are also called club fungi • Many basidiomycetes are decomposers of wood © 2011 Pearson Education, Inc. Figure 31.UN05 Chytrids Zygomycetes Glomeromycetes Ascomycetes Basidiomycetes Figure 31.18 Shelf fungi Puffballs emitting spores Maiden veil fungus (Dictyphora) • The life cycle of a basidiomycete usually includes a long-lived dikaryotic mycelium • In response to environmental stimuli, the mycelium reproduces sexually by producing elaborate fruiting bodies called basidiocarps • Mushrooms are examples of basidiocarps • The numerous basidia in a basidiocarp are sources of sexual spores called basidiospores © 2011 Pearson Education, Inc. Figure 31.19 Key Dikaryotic mycelium PLASMOGAMY Haploid (n) Dikaryotic (n n) Diploid (2n) Mating type () Mating type () Haploid mycelia SEXUAL REPRODUCTION Gills lined with basidia Dispersal and germination Basidiospores (n) Basidium with four basidiospores Basidium Basidia (n n) Basidium containing four haploid nuclei KARYOGAMY MEIOSIS 1 m Basidiospore Diploid nuclei Basidiocarp (n n) Figure 31.20 • Basidiomycetes can produce mushrooms quickly • Some species may produce “fairy rings” Imagine a fungi-free world… Concept 31.5: Fungi play key roles in nutrient cycling, ecological interactions, and human welfare • Fungi interact with other organisms as decomposers, mutualists, and pathogens © 2011 Pearson Education, Inc. Fungi as Decomposers/Nutrient recylers • Fungi are efficient decomposers of organic material including cellulose and lignin • Fungi are also used in bioremediation projects © 2011 Pearson Education, Inc. Fungi as Mutualists © 2011 Pearson Education, Inc. Fungus-Plant Mutualisms • Mycorrhizae are enormously important in natural ecosystems and agriculture – Plants harbor harmless symbiotic endophytes, fungi that live inside leaves or other plant parts – Endophytes make toxins that deter herbivores and defend against pathogens – Most endophytes are ascomycetes © 2011 Pearson Education, Inc. Figure 31.21 RESULTS Leaf area damaged (%) Leaf mortality (%) Endophyte not present; pathogen present (EP) Both endophyte and pathogen present (EP) 30 20 10 0 EP EP 15 10 5 0 EP EP Fungianimal symbiosis Lichens • A lichen is a symbiotic association between a photosynthetic microorganism and a fungus – The photosynthetic component is green algae or cyanobacteria – The fungal component is most often an ascomycete • The symbioses are so complete that lichens are given scientific names © 2011 Pearson Education, Inc. Figure 31.23 A foliose (leaflike) lichen Crustose (encrusting) lichens A fruticose (shrublike) lichen Lichen anatomy Ascocarp of fungus 50 m Fungal hyphae Algal layer Fungal hyphae Algal cell Soredia • Lichens are important pioneers on new rock and soil surfaces • Lichens may have helped the colonization of land by plants 550–600 million years ago © 2011 Pearson Education, Inc. Fungi as Pathogens • About 30% of known fungal species are parasites or pathogens, mostly on or in plants • Each year, 10% to 50% of the world’s fruit harvest is lost due to fungi • Some fungi that attack food crops are toxic to humans © 2011 Pearson Education, Inc. Figure 31.25 (b) Tar spot fungus on maple leaves (a) Corn smut on corn (c) Ergots on rye Fungi caused Salem Witch Trials? • Ergotism is characterized by gangrene, nervous spasms, burning sensations, hallucinations, and temporary insanity – Ergots contain lysergic acid, the raw material for LSD © 2011 Pearson Education, Inc. Global amphibian populations are down due to fungal infection (mycosis) California Sixty Lake Basin N Yellow-legged frogs killed by B. dendrobatidis infection Key Boundary of chytrid spread Lake status in 2009: 2007 Frog population extinct Treatment lake: frogs treated with fungicides and released Practical Uses of Fungi • Humans eat many fungi and use others to make cheeses, alcoholic beverages, and bread • Some fungi are used to produce antibiotics for the treatment of bacterial infections – For example, the ascomycete Penicillium © 2011 Pearson Education, Inc. Fungal production of antibiotic Staphylococcus Penicillium Zone of inhibited growth Figure 31.UN06 Fungal Phylum Distinguishing Features of Morphology and Life Cycles Chytridiomycota (chytrids) Flagellated spores Zygomycota (zygote fungi) Resistant zygosporangium as sexual stage Glomeromycota (arbuscular mycorrhizal fungi) Arbuscular mycorrhizae formed with plants Ascomycota (ascomycetes, or sac fungi) Sexual spores (ascospores) borne internally in sacs called asci; vast numbers of asexual spores (conidia) produced Basidiomycota (basidiomycetes, or club fungi) Elaborate fruiting body (basidiocarp) containing many basidia that produce sexual spores (basidiospores) Figure 31.UN08 Figure 31.UN09 Figure 31.UN10