Fungi are diverse and widespread



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Fungi are diverse and widespread

  • Fungi are diverse and widespread

  • 100,000 described species

  • Really as many as 1.5 MILLION?

  • Honey mushroom - 2000 years old, 1,800 football fields (underground) or a yeast cell

  • Essential in ecosystem nutrient recycling

  • Mycology





Despite their diversity, fungi share key traits, most importantly the way in which they derive nutrition

  • Despite their diversity, fungi share key traits, most importantly the way in which they derive nutrition



Fungi are heterotrophs and absorb nutrients from outside of their body

  • 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

  • The versatility of these enzymes contributes to fungi’s ecological success



Fungi exhibit diverse lifestyles:

  • Fungi exhibit diverse lifestyles:

    • Decomposers
    • Parasites
    • Mutualists


The most common body structures are multicellular filaments and single cells (yeasts)

  • The most common body structures are multicellular filaments and single cells (yeasts)

  • Some species grow as either filaments or yeasts; others grow as both



The morphology of multicellular fungi enhances their ability to absorb nutrients

  • 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 unique fungi have specialized hyphae called haustoria that allow them to penetrate the tissues of their host

  • Some unique fungi have specialized hyphae called haustoria that allow them to penetrate the tissues of their host











Mycorrhizae are mutually beneficial relationships between fungi and plant roots

  • Mycorrhizae are mutually beneficial relationships between fungi and plant roots

  • Two types:



Mycorrhizae are mutually beneficial relationships between fungi and plant roots

  • 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

  • Arbuscular mycorrhizal fungi extend hyphae through the cell walls of root cells and into tubes formed by invagination of the root cell membrane



Fungi propagate themselves by producing vast numbers of spores, either sexually or asexually

  • Fungi propagate themselves by producing vast numbers of spores, either sexually or asexually

  • Fungi have different types of life cycles









Fungal nuclei are normally haploid, with the exception of transient diploid stages formed during the sexual life cycles

  • Fungal nuclei are normally haploid, with the exception of transient diploid stages formed during the sexual life cycles

  • Sexual reproduction requires the fusion of hyphae from different mating types (“sexes”)

  • Fungi use sexual signaling molecules called pheromones to communicate their mating type (like many animals including primates!)



Plasmogamy is the union of two parent mycelia

  • Plasmogamy is the union of two parent mycelia

  • In most fungi, the haploid nuclei from each parent do not fuse right away; they coexist in the mycelium, called a heterokaryon

  • The different nuclei may even swap DNA similar to “crossing over”.



Hours, days, or even centuries may pass before the occurrence of karyogamy, nuclear fusion (kary = nucleus)

  • Hours, days, or even centuries may pass before the occurrence of karyogamy, nuclear fusion (kary = nucleus)

  • During karyogamy, the haploid nuclei fuse, producing diploid cells

  • The diploid phase is short and undergoes meiosis (halving!), producing haploid spores



In addition to sexual reproduction, many fungi can reproduce asexually

  • In addition to sexual reproduction, many fungi can reproduce asexually

  • Molds produce haploid spores by mitosis and form visible mycelia





Other fungi that can reproduce asexually are yeasts, which inhabit moist environments

  • Other fungi that can reproduce asexually are yeasts, which inhabit moist environments

  • Instead of producing spores, yeasts reproduce asexually by simple cell division and the pinching of “bud cells” from a parent cell





Many molds and yeasts have no known sexual stage

  • Many molds and yeasts have no known sexual stage



Fungi and animals are more closely related to each other than they are to plants or other eukaryotes

  • Fungi and animals are more closely related to each other than they are to plants or other eukaryotes



Fungi, animals, and their protistan relatives form the opisthokonts clade

  • Fungi, animals, and their protistan relatives form the opisthokonts clade





The oldest undisputed fossils of fungi are only about 460 million years old

  • The oldest undisputed fossils of fungi are only about 460 million years old



Fungi were among the earliest colonizers of land and probably formed mutualistic relationships with early land plants

  • Fungi were among the earliest colonizers of land and probably formed mutualistic relationships with early land plants







Chytrids (phylum Chytridiomycota) are found in freshwater and terrestrial habitats

  • 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







Until recently, systematists thought that fungi lost flagella only once in their evolutionary history

  • Until recently, systematists thought that fungi lost flagella only once in their evolutionary history

  • Molecular data indicate that some “chytrids” are actually more closely related to another fungal group, the zygomycetes; chytrids are a paraphyletic group





The zygomycetes (phylum Zygomycota) exhibit great diversity of life histories

  • 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

  • Zygosporangia, which are resistant to freezing and drying, can survive unfavorable conditions





The life cycle of black bread mold (Rhizopus stolonifer) is fairly typical of the phylum

  • The life cycle of black bread mold (Rhizopus stolonifer) is fairly typical of the phylum



Some zygomycetes, such as Pilobolus, can actually “aim” their sporangia toward conditions associated with good food sources

  • Some zygomycetes, such as Pilobolus, can actually “aim” their sporangia toward conditions associated with good food sources

  • Toward light = grass = cows = dispersal!

  • 25m/sec = 1,million times its length/sec.

  • Fastest aerial acceleration in nature







The glomeromycetes (phylum Glomeromycota) were once considered zygomycetes

  • The glomeromycetes (phylum Glomeromycota) were once considered zygomycetes

  • They are now classified in a separate clade

  • Glomeromycetes form arbuscular mycorrhizae









Ascomycetes (phylum Ascomycota) live in marine, freshwater, and terrestrial habitats

  • Ascomycetes (phylum Ascomycota) live in marine, freshwater, and terrestrial habitats



Ascomycetes (phylum Ascomycota) live in marine, freshwater, and terrestrial habitats

  • 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 (phylum Ascomycota) live in marine, freshwater, and terrestrial habitats

  • 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 are commonly called sac fungi

  • Ascomycetes vary in size and complexity from unicellular yeasts to elaborate cup fungi and morels



Ascomycetes include plant pathogens, decomposers, and symbionts

  • Ascomycetes include plant pathogens, decomposers, and symbionts

  • Ascomycetes reproduce asexually by enormous numbers of asexual spores called conidia



Ascomycetes include plant pathogens, decomposers, and symbionts

  • 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

















Mycoses - Ringworm, indoor molds (sick buildings), athelete’s foot, Candida (diaper rash and worse)Candida albicans

  • Mycoses - Ringworm, indoor molds (sick buildings), athelete’s foot, Candida (diaper rash and worse)Candida albicans

  • Fusarium (grains; Jurgenson research)

  • Cryptococcus (pigeon poop)

  • Ergot!















































Basidomycetes (phylum Basidiomycota) include mushrooms, puffballs, and shelf fungi, mutualists, and plant parasites

  • Basidomycetes (phylum Basidiomycota) include mushrooms, puffballs, and shelf fungi, mutualists, 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













The life cycle of a basidiomycete usually includes a long-lived dikaryotic mycelium

  • 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 call basidiocarps

  • Mushrooms are examples of basidiocarps

  • The numerous basidia in a basidiocarp are sources of sexual spores called basidiospores















Fungi are efficient decomposers

  • Fungi are efficient decomposers

  • They perform essential recycling of chemical elements between the living and nonliving world



Fungi form mutualistic relationships with plants, algae, cyanobacteria, and animals

  • Fungi form mutualistic relationships with plants, algae, cyanobacteria, and animals

  • All of these relationships have profound ecological effects



Mycorrhizae are enormously important in natural ecosystems and agriculture

  • Mycorrhizae are enormously important in natural ecosystems and agriculture

  • Plants harbor harmless symbiotic endophytes that live inside leaves or other plant parts

  • Endophytes make toxins that deter herbivores and defend against pathogens





Some fungi share their digestive services with animals

  • 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”







A lichen is a symbiotic association between a photosynthetic microorganism and a fungus in which millions of photosynthetic cells are held in a mass of fungal hyphae

  • A lichen is a symbiotic association between a photosynthetic microorganism and a fungus in which millions of photosynthetic cells are held in a mass of fungal hyphae











The fungal component of a lichen is most often an ascomycete

  • The fungal component of a lichen is most often an ascomycete

  • Algae or cyanobacteria occupy an inner layer below the lichen surface





The algae provide carbon compounds, cyanobacteria provide organic nitrogen, and fungi provide the environment for growth

  • The algae provide carbon compounds, cyanobacteria provide organic nitrogen, and fungi provide the environment for growth

  • The fungi of lichens can reproduce sexually and asexually

  • Asexual reproduction is by fragmentation or the formation of soredia, small clusters of hyphae with embedded algae



Lichens are important pioneers on new rock and soil surfaces

  • Lichens are important pioneers on new rock and soil surfaces

  • Lichens are sensitive to pollution, and their death can be a warning that air quality is deteriorating



About 30% of known fungal species are parasites or pathogens, mostly on or in plants

  • About 30% of known fungal species are parasites or pathogens, mostly on or in plants

  • Some fungi that attack food crops are toxic to humans

  • Animals are much less susceptible to parasitic fungi than are plants

  • The general term for a fungal infection in animals is mycosis



Humans eat many fungi and use others to make cheeses, alcoholic beverages, and bread

  • 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

  • Genetic research on fungi is leading to applications in biotechnology

    • For example, insulin-like growth factor can be produced in the fungus Saccharomyces cerevisiae














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