Fungi Flashcards
(25 cards)
What are the 2 ways fungi can be classified
- Morphology - by the structures produced during sexual reproduction
- By evolutionary relationships (DNA sequence)
What does traditional classification of fungi have to structurally consider
- Orphological features may not be produced constitutively
- Different morphology of sexual vs asexual structures
- Dual nomenclature (different scientific names for sexual/asexual morphologies)
- Dimorphism seen in numerous genera
What does molecular classification rely on
Relies on PCR-based amplification and sequencing
and/or genome sequencing, followed by comparison of sequences with those in publicly-available databases:
• enables genetically similar organisms to be grouped together
• enables inferences about ‘best’ treatment options
What are two types of fungal cellular morphology
- Filamentous fungi
- Non-filamentous fungi e.g. yeasts
What do filamentous fungi have that’s important
- Fungi consists of thin, thread-like filaments called hyphae
- Some hyphae contain cross-walls (septa) which divides them internally into distinct uni-nuclear units
What do non-filamentous fungi yeast look like
Yeasts can look like bacteria and form colonies on plates
- unicellular round or oval cells
What does dimorphism mean
Able to switch/exist as both morphological forms
What are the different roles of hyphae
- vegetative hyphae = region that absorbs nutrients
• aerial hyphae = region that bear reproductive structures/spores
• hyphae mass = mycelium
What are the 4 structures of hyphae (top to bottom)
- Growing tip
- Absorption zone
- Storage zone
- Senescence zone
What are hyphal wall made out of
- Chitin
- provides rigidity
Why does the tip of hyphae have vesicles
- The vesicles are important for growth
- Help with reorganization of the cell was when broken from growth
What is the hyphal plasma membrane made out of
- Ergosterol
How do fungi get their food?
- Fungi are chemoheterotrophs
- They do not make their own food (like some bacteria) but instead obtain their nutrients from preformed sources of organic carbon
- By using enzymes to breakdown organic compounds
- And store their food as glycogen
What are fungi role in the ecosystem
Principal decomposers (saprotrophs)
How do fungi dimorphic switch
- Due to triggers
- e.g. temperature, CO2 levels, pH
- ## Ascomycetes switch from a multicellular form (hyphae) at 25°C to unicellular form (yeast) at 37°C
Give 2 reasons why fungi switch morphology
- Hyphae to yeast - switch enables sustained growth of species inside host immune cells
- Yeast to hyphae - when entering a host to aid tissue penetration
4 steps
Asexual reproduction life cycle
- spore-producing structures (n)
- spores (n)
- germination
- mycelium (n)
9 steps
Sexual reproduction life cycle
- dikaryotic stage (n+n)
- karyogamy (fusion of nuclei)
- diploid stage (2n)
- meiosis
- spore-producing structures (n)
- spores (n)
- germination
- mycelium
- plasmogamy (fusion of cytoplasm)
3 mechanisms for asexual reporduction
- Hyphal fragmentation
- Spore production
- Budding (yeast)
What are the 2 types of asexual spores
- conidiospore (conidium/conidia) (on surface and not within a sac) e.g. Penicillium, Aspergillus
- sporangiospore (sporangium/sporangia) (spores within a sac) e.g. Rhizopus (bread mold fungus)
3 ways fungi can be pathogenic in humans
- Superficial infections - Infections of the outer layer of the skin, the hair and nails. Examples: athlete’s foot, ringworm
- Subcutaneous fungal infections - Infections usually occur in deeper layers of the skin and sometimes even reach the underlying bone. Examples: Mycetoma (fungi in soil)
- Systemic mycoses - Infection often occurs via inhalation of fungal spores by individuals with a weakened immune system.
Examples: Thrush caused by Candida spp
3 ways fungi can be pathogenic in plants
- Rice blast disease caused by Magnaporthe oryae
- Wheat stem rust (Puccinia graminis)
- Late potato blight (Phytophthora infestans)
How does the fungi mycorrhizae help plants
- Fungus functions like a root by growing in the soil and absorbing nutrients for the plant, while the plant provides it with sugars for energy
- Approx. 90% of all plants develop mycorrhizae
What are the 2 types of mycorrihizae
- Ectomycorrihiza - grows between cells, fungus is ascomycota
- Arbuscular mycorrihiza - grows inside cells, fungus is zygomycota
