11 - Fungal biology* Flashcards
Fungi
Diverse group of eukaryotic organisms that are spore-bearing, have absorptive nutrition, do not photosynthesise, and normally reproduce both sexually and asexually. Vary greatly in size and shape (most fungi underground as hyphae)
Structure of fungi cells
Contain nucleus, mitochondria, ER, ribosomes, microfilaments, microtubules, plasma membrane and cell wall
Hyphae
- Tubular branching filament
- Can be either:
- Aseptate (coenocytic): protoplasm streams through the hyphae
OR - Septate: have a septum with pores to allow streaming
Mycelium
- A mass of branching hyphae
- A type of thallus (body or vegetative structure of fungus) - extensionf
Mold
Fungi producing filamentous growth
Exceptions to characteristics of fungi
- Yeasts are unicellular, bud, and do not have a mycelial stage
- Some pathogenic fungi are dimorphic induced by temp change (mycelial form outside host, yeast form in host)
What are hyphal cell walls composed of
- chitin (NAG)
- Glucan (polysaccharide)
Heterotrophic nutrition
Use reduced, preformed organic molecules as carbon source
Osmotrophic
soluble nutrients are absorbed through the cytoplasmic membrane
Saprophytic
derive nutrition from degradation of dead organic matter
Example of predatory fungus
Nermatode trapping fungus
Production of Spores
- both sexual and asexual spores may be produced
- asexually on mycelium
- sexually following mating
Motility
Most non motile (besides Chytridiomycota)
- exist in water or moist areas
Life cycle of fungi
Have simple to complex life cycles involving vegetative growth (mycelium) interspersed with asexual and/or sexual reproduction
Characteristics of fungi
- Eukaryotic
- Basic units called hypae
- Cell walls composed of chitin and glucan
- Heterotrophic and osmotrophic nutrition
- Produce spores
- Non motile
Why are fungi hard to classify
due to having both sexual and asexual reproduction (same fungi has two different names)
What are the six major groups (based on molecular analysis)
- Chytridiomycota
- Zygomycota
- Glomeromycota
- Ascomycota
- Basidiomycota
- Microsporidia
types of asexual reproduction
- Also called anamorph
- Hyphal growth (vegetative growth)
- Hyphal fragments transplanted or broken from the body of the fungus can continue to grow
- Asexual spore formation
- Budding (yeasts)
Types of asexual spore formation
- Sporangiospores (produced in a membrane enclosed structure called a ‘sporangium’)
- Conidiospores (spores born on tips or sides of ‘conidiophores’ – not enclosed in a membrane)
types of sexual reproduction
- Also called telomorph
- Motile gametes
- Gametangial contact (Contact between egg and antheridium)
- Fusion of non motile male and female structures
- Fusion of compatable vegetative hyphaa
Zygomycota
- Most are saprophytes
- a few are plant and animal parasites
- production of foods (e.g. tempeh), antibiotics and other drugs, meat tenderiser, and yellow food colouring
Characteristics of zygomycota
- Form coenocytic hyphae containing numerous haploid nuclei
- Sexual reproduction requires compatible opposite mating types +/- (‘heterothallic’)
and produces zygosporangium (contains zygospore) - asexual reproduction is by formation of a sporangium that produces sporangiospores
Example of zygomycota
Rhizopus stolonifera (bread mold)
Ascomycota
- Cup shape
- Most are saprophytes
- A few are plant and animal pathogens
- Terriestrial and aquatic
Characteristics of Ascomycota
- Septate hyphae
- Sexual reproduction: heterothallic or homothallic (self fertile), produces ascospores
- Asexual reproduction: formation of conidiospores on conidiophores
Examples of Ascomycota
Aspergillus spp, yeasts and truffles
Basidiomycota
- Most are saprophytes
- A few plant and animal pathogens
- Primarily terrestrial
- includes edible mushrooms
- many produce hallucinogenic compounds
Characteristics of Basidiomycota
- Usually septate hyphae
- Sexual reproduction: heterothallic, produces basidiospores
- Asexual reproduction is rare
Examples of Basidiomycota
Common mushrooms (club fungi)
What are the ecological roles of fungi
- Decomposers
- Disease agents
- Symbiosis
- Products and industry
Fungi as decomposers
- Break down complex macromolecules to simple molecules (e.g. cellulose)
- Mineralise organic matter, returning important nutrients (e.g. C, N, P) to the environment
- Convert organic matter into fungal biomass (which becomes food for other organisms)
Disease agents
- Plants
- animals and humans (superficial, cutaneous, subcutaneous, systemic infections)
Example of systemic fungal disease
Histoplasmosis
Example of superficial fungal disease
Black piedra
Example of cutaneous fungal disease
Tinea pedis (athlete’s foot)
Example of subcutaneous fungal disease
Sporothrix schenckii
Two examples of symbiosis
- Lichens: association between Ascomycete + alga or cyanobacterium
- Mycorrhizae: association between Ascomycete or Basidiomycete + plant
Examples of fungus in products and industry
- Foods/beverages (bread, wine, beer, cheeses)
- Industrial chemicals (organic acids, alcohols)
- Pharmaceuticals e.g. antibiotics (penicillin)
