Fungill Lecture 24 - Chapter 31: Fly Agaric (Amanita muscaria) - Thunder Bird Falls, Alaska, 5 July 2014
Opening Quote
Joshua 9:12 NIV
"This bread of ours was warm when we packed it at home on the day we left to come to you. But now see how dry and moldy it is."
Taxonomic Groups
Chytrids (Phylum Chytridiomycota)
Characteristics:
Most are unicellular.
Structure:
Hyphae and Mycelia:
Lack hyphae and mycelia but can form a body-like thallus and root-like rhizoids.
Zoospore
Definition:
A motile, asexual spore that is capable of swimming in an aquatic environment using flagella.
Characteristics of Zoospores:
Typically have one flagellum, though some may possess multiple flagella.
Function: Used to disperse and find hosts.
General Characteristics of Chytrids
Ecology:
Most are decomposers, but many are parasites or mutualists (none infect humans).
Ubiquitous in aquatic and terrestrial environments, including deep-sea hydrothermal vents.
Anaerobic species aid in digestion in sheep and cattle.
Chytridiomycosis
Definition:
A fungal infection in the skin of amphibians.
Causes of Chytridiomycosis:
Specifically caused by two species of Batrachochytrium.
Notable Impact: Caused a decline of 7% of amphibian species since the 1980s.
Zygote Fungi (Zygomycetes - Phylum Zygomycota)
Characteristics:
Most are multicellular.
Have hyphae; spores lack a flagellum.
Zygosporangium
Definition:
A thick-walled, diploid structure (2n) formed sexually from a zygote by the fusion of two haploid hyphal extensions (1n).
Zygosporangium and diploid zygospores (2n) are produced during harsh environmental conditions and can resist these conditions for years.
Zygospores
Diploid zygospores (2n) later germinate and release haploid spores (1n).
Process: Neighboring mycelia can fuse, leading to the fusion of haploid nuclei of opposite mating types.
Subphyla of Zygote Fungi
Zoopagomycetes:
Most are parasites or symbionts of animals.
Mucoromycetes:
Most are parasites or symbionts of other fungi or plants.
Examples include Fly Death Fungi (Entomophthora muscae) and Bonnet Mold (Spinellus fusiger).
Sac Fungi (Ascomycetes - Phylum Ascomycota)
Characteristics:
Most are multicellular and have hyphae.
Spores lack a flagellum; can reproduce asexually or sexually.
Conidiophore
Definition:
The tip of a hypha that produces asexual spores called conidia.
Asexual Reproduction in Sac Fungi
Reproduces via conidiospores including structures like the Penicillium phialide and Aspergillus vesicle.
Conidia
Singular form: conidium; can occur in clusters or long chains.
Can also play a role in sexual reproduction, as seen in Aspergillus fumigatus.
Ascocarp
Definition:
A diploid "sac" (2n) with reproductive structures, formed sexually by hyphae.
Types of Ascocarps
Shaped like a cup, flask, or sphere.
Examples include Cleistothecium, Perithecium, and Apothecium.
Asci: Each ascocarp contains millions of asci, with each ascus containing 4 or 8 ascospores (1n).
Mutualistic Associations
Approximately 40% of species of sac fungi form mutualistic associations with a green alga or cyanobacterium in lichens.
Examples include Brown-eyed Wolf Lichen (Letharia columbiana), Common Sunburst Lichen (Xanthoria parietina), Tree Lungwort (Lobaria pulmonaria), Oakmoss (Evernia prunastri), and Lace Lichen (Ramalina menziesii).
Club Fungi (Basidiomycetes - Phylum Basidiomycota)
Characteristics:
Most are multicellular and have hyphae.
Spores lack a flagellum and are the most conspicuous group of fungi.
Basidiocarp
Definition:
A large, haploid reproductive structure (1n), formed sexually, consisting of club-shaped diploid basidia (2n) that produce haploid basidiospores (1n).
Structure of Basidiocarp
Components include gills, cap, gill, and stipe (stalk), as well as basidia and basidium along with the spores.
Biodiversity in Club Fungi
Basidia typically located in gills on the ventral surface of the basidiocarp in many species, although not all species produce a basidiocarp.
Ecological Role of Club Fungi
Most are decomposers; some act as parasites or mutualists, as seen in figures like Tricholomopsis aurea.
Ecological Roles: Decomposition
Role of fungi in breaking down organic compounds, which releases nutrients into the environment.
Crucial in both Carbon (C) and Nitrogen (N) cycles that sustain life.
Ecological Roles: Mutualism
Many plants and insects host symbiotic fungi, which absorb nutrients from the host and provide benefits to them.
Benefits of Fungi to Plants
Enhanced water and nutrient absorption.
Enhanced stress tolerance to heat, drought, salt, or heavy metals.
Enhanced resistance against herbivores or pathogens by producing toxins.
Benefits of Fungi to Animals
Serve as a protective shield from predators and pathogens, as in the example of stinkbug eggs.
Break down plant matter in intestines of mammals, including humans.
Leafcutter Ants and Fungi
Leafcutter ants farm a club fungus, which feeds on the leaves they provide.
Fungus provides the ants with nutrients at the tips of their hyphae.
Lichens
Definition:
A mutualistic partnership between a fungus and a photosynthetic green alga or cyanobacterium.
Components of Lichens
The fungal component drives structure and provides shelter for the photosymbiont (mostly sac fungi).
The photosymbiont component typically resides under the surface of the fungal body, supplying carbon and nitrogen compounds to the fungus, constituted by 90% green algae and 10% cyanobacteria.
Anatomy of a Lichen
Components include ascocarp of fungus, soredia, fungal hyphae, algal layer, and algal cells.
Mycorrhizae
Definition:
Fungi associating with the roots of plants, which facilitate nutrient absorption.
Associations
Hyphae at tips of plant roots greatly assist in water and nutrient uptake.
Overall prevalence: Mycorrhizae are found in 95% of plant species.
Parasitism in Fungi
Approximately 5% of fungal species are parasitic towards plants, destroying a significant proportion of agricultural crops.
Animal Parasitism
Less than 1% of fungal species parasitize animals.
Notable example: specific chytrids are significantly harming amphibian populations.
Human Pathogenic Examples
Ringworm, jock itch, and athlete’s foot - caused by several species of sac fungi that feed on moist, dead skin.
Oral thrush and vaginal candidiasis - caused by Candida spp. which may overgrow when the immune system is weakened.
Valley fever - caused by Coccidioides spp., fungi from inhaled soil spores.
Human Uses of Fungi
Food Sources:
Mushrooms (club fungi), morels and truffles (sac fungi) are commonly consumed.
Yeast (sac fungi) utilized in bread production and alcoholic beverages.
Medicinal Applications
Fungi like Penicillium spp. are vital for antibiotics, such as penicillin.
Quiz Preparation
Study for a quiz over lectures 23-24 (Chapter 31).