UNIT 1: KINGDOM FUNGI (24) Flashcards
Defining Characteristics:
- Mycology: the scientific study of fungi
- Fungi appeared in their modern form about 653 million years ago
- Unicellular or multicellular
- More Closely related to animals than plants
- 1.5 million fungal species
- Heterotroph
- Diploids have one copy or version of every gene
- Haploids of two copies of versions of every game
Eukaryotic Fungal Cells
- Nuclear DNA + some components resemble bacterial plasmids
- Typical organelles ( mitochondria, golgi, endoplasmic retic umum, etc)
- Don’t have chloroplasts because they don’t deal with photosynthesis (don’t make their own food!!)
Cell Wall and Membranes
- Strengthens and supports cells
- Makes harem non-motile (inability to move)
- Consists of: wall and membrane
- Wall = chitin and glucans
- Membrane = ergosterol
- Cells may have more than one nucleus
- Monokaryotic (n or 2n) vs. Dikaryotic (n+n)
- Dikaryotic cells are typically haploid.
- Cells are sometimes separate by cell walls called septa (septated) or have merged together with nothing separating the cytoplasm (coenocytic)
Hetero
- Hyphae have nuclei that are derived from two different individuals (product of sexual reproduction)
Homo
- Hyphae have nuclei from one individual (product of asexual reproduction)
Fungal bodies can exist in two stages:
Vegetative Body, and Reproductive Body
The Vegetative Body Consists Of:
- Hypha(e): a filament of cells (may be septate or coenocytic)
- Mycelium: collection of hyphae (digests materials)
Reproductive body:
- Build for reproduction
- May use fragmentation, budding, or spores
Fragmentation
- Breaking off a part of the hypha and it is asexual
Budding
- Bulge forms on the side of the cell, and the bud detaches itself from the mother cell (making clones)
Spores:
- This is how fungi reproduce
- Are ALWAYS haploid (1n)
- May result from sexual or asexual reproduction
- Build for dispersal
- Originally flagellated
- Most are dispersed by wind, insects, animals
- Spores are released through several structures
Sporangium
- Special reproductive sac that grows at the end of a hypha
Conidiospores
- Spores that are released directly from the tip or side of the hypha with no sac
Sexual Reproduction
- Typically occurs only in adverse environmental conditions
Four stages:
1) Plasmogamy 2) karyogamy 3) Meiosis 4) Spores
1) Plasmogamy:
- Two haploid hyphae come in contact with each other
- Cells from hyphae fuse
- Results in a dikaryotic cell with 2 haploid nuclei
- No sperm and no egg
- No male and no female
2) Karyogamy:
- “Nuclear marriage”
- The two haploid nuclei fuse to form one diploid one ???
3) Meiosis:
- The diploid nucleus divides into 4 haploid nuclei
- This occurs in a specialized structure called a gametangium
4) Spores:
- The haploid nuclei form spores which are dispersed into the environment
Fungal Metabolism
- Fungi thrive in environments that are moist and slightly acidic, and can grow with or without light
- Fungi can break down cellulose
Oxygen Requirements:
- Obligate aerobes
- Facultative aerobes
- Obligate anaerobes
Saprophytes
Consume decaying/ decomposing organic matter
Parasites
Ectoparasites (pathogens such as ticks, fleas, lice, parasitic flies and mites) that grow into plants and animals while they are still living
Nutrient cycling
- Saprophytes decompose dead organic tissues
- Release N and P back into the environment for other organisms to use
- Able to break down large, recalcitrant molecules
- Interactions with other organisms
- Helpful symbiotic interactions
Fungal Diversity
- New phylogeny via sequencing of ribosomal RNA
- Chytridiomycota
- Zygomycota
- Ascomycota
- Basidiomycota
- Glomeromycota
Taxonomic Terminology
- -mycota is used to designate a phylum
- Or is used informally to refer to all members of the phylum
Phylum Chytridiomycota
- Most primitive of rue fungi
- Unicellular mostly
- Some coenocytic multicellular taxa
- Only fungi that have retained flagella
- Gametes and zoospores use a single flagellum to swim
- Some are saprophytes, but most are parasites
Batrachochytrium
A fungus that causes the disease chytridiomycosis in amphibians
Chytridiomycosis (chytrid)
Responsible for the worldwide decline in amphibian populations
Rhizophydium
Plant and algal infections
Phylum Zygomycota
- Most saprobes, some parasitic
- Bread mold: Rhizopus stolonifera
- Complex sexual reproduction
- Two opposing mating strains (type + and type -)
Hyphae strains meet:
1) Plasmogamy forms a zygosporangium
2) Karyogamy
3) Meiosis
4) Spores are ejected by a stalk called a sporangium (this gives black mold its color)
Phylum Ascomycota
- The “sac” fungi
- Ascus (plural, asci), a sac-like structure that contains spores
- Contain about 75% of the known fungi
- Include: bread yeasts, common molds, Penicillium, cup fungi, morels
- Hyphae septate
Phylum Ascomycota Asexual Reproduction:
- Conidiospores from a conidiophore
- Sexual reproduction:
- Two “strains” of hyphae
- “Male” strain produces an antheridium
- “Female”strain develops an ascogonium
Phylum Ascomycota Sexual Reproduction:
1) The antheridium and ascogonium fuse (plasmogamy), and then a multicellular, dikaryotic fruiting body called an ascocarp forms. It is full of asci sacs
2) Karyogamy occurs in
each ascus
3) Meiosis occurs in each ascus
4) Eight haploid ascospores form and are dispersed
Phylum Basidiomycota
- The “club” fungi
- Club-shaped structures called basidia (singular, basidium) are terminal cells of hyphae
- Most familiar fungi
- Mushrooms, puffballs, jelly fungi
- Plant pathogens such as rusts and smuts
Phylum Basidiomycota Sexual Reproduction
1) Two primary (n) mycelium fuse (plasmogamy) to form a secondary (n+n) mycelium
- Multicellular, eukaryotic fruiting body called a basidiocarp forms (mushroom). It is full of basidia in “gills.”
2) Karyogamy occurs in
each basidium.
3) Meiosis occurs in each basidium
4) Four haploid basidiospores form and are dispersed
Phylum Glomeromycota
- Newest phylum
- Coenocytic and asexual
- All obligate symbionts with plant roots
- Arbuscular Mycorrhizae: shrub and grass plants, hyphae enter root cells
- Ectomycorrhizae: tree plants, hyphae DO NOT enter root cells
Mutualist Fungi
- Mycorrhizae (fungi roots) are mutualistic relationships between fungi and plants
- Found on the roots of about 90% of all known vascular plant species
- They help the plant take up water, and in return get to live within the tough roots and get nutrients
- Endophytic fungi live in the intercellular spaces inside plants
- Fungi protect their hosts by producing toxins
- Lichens are symbiotic associations between a fungus and a photosynthetic partner
- Liches have invaded the harshest habitats, where they are often the first colonists
- Leaf-cutter Attini ants have domesticated fungi which the keep in underground garden
Animal Parasites:
- Ectoparasites In Animals
- Hyphae Called Haustoria Penetrate the host tissue and break it down
Amphibians/Insects Parasites:
- Athlete’s foot and thrush in humans
Plant Parasites:
- Smut and Dutch elm disease
- Corn disease
