Fungi Flashcards
What are the main characteristics of fungi?
They are heterotrophs therefore need to obtain carbon from another organic source
What is the study of fungi called?
Mycology
Describe the structure of a fungal cell?
All the same organelles as a plant and animal cell with the addition of a bud, septum and bud scar
What are the 2 types of antifungals used to fight fungi?
Polyene Antibiotics
Azole antifungals
What do azole antifungals target?
The fungal cell membrane
How do the azoles work?
They work on 2 fronts:
By interrupting the lipid bilayer
By poisoning the cell through the build-up of toxic sterols
What effect to do azoles have on C.albicans?
They cause the cells to crenellate and shrink in on themselves, due to disruption of the lipid bilayer
They are no longer functional
What do the Polyene class do?
They create a ‘death ring’
How does the Polyene Amphotericin B work?
Enlarges itself within the membrane
Binds to ergesterol in multiple locations
It then creates channels once enough of them have bound to the ergosterol
Suggesting 8 molecules bound (‘8 member death ring’) forms an ion channel
If an ion channel is produced by a Polyene class antifungal, what happens?
Ions leak out of the cell through the ion channel
This changes the osmotic potential
So water moves out of the cell because the water potential is lower outside the cell
Leaving a crenelated cell
What are dimorphic fungi?
Fungi that can grow to be either filamentous or yeast depending on what conditions you grow them in
What are the 2 structural phases of dimorphic fungi?
Yeast- unicellular
Filamentous- hyphae
List the properties of Candida albicans
Dimorphic
Opportunistic pathogen- only strikes as pathogen when the conditions are correct
Commences in the yeast phase- Manageble by hygiene and immune system
Only becomes invasive when in the filamentous phase
How can spores reproduce?
Either sexually or asexually
Describe the structure of a spore
They have a nucleus, dehydrated cytoplasm, glycogen that forms a coat and a thick spore wall
What are the 2 main types of asexual reproduction of spores?
Conidium- individual spores
Sporangiospores- multiple spores in a sac
Where are conidia found?
Found on the end of a hyphae (conidiophore)
How do penicillium conidia reproduce?
Break off the conidiophores and disperse into the air
How do aspergillus conidia structured?
Aspergillus have a vesicle that terminates the hyphae
Protrusions from that are the conidiophores
At end of conidiophores are conidia
How do sporangium reproduce?
Sporangiospores in the sporangium
Sporangium sit on a sporangiophore
When spoangiospores are released sporangium wall splits
Give the 2 types of fungi hat can reproduce
Imperfect fungi- asexual spores
Perfect fungi- capable of asexual AND sexual reproduction (sexual spores)
What are the 3 main types of sexual spores?
Zygomytes
Ascomycetes
Basidomycetes
How do zygomycetes reproduce?
Fusion of hyphae from two individual zygospores
Zygospore develops develops a thick cell wall which can be dispersed in the air and spread
For example, bread mould
How do Ascomycetes reproduce?
Sexual spores in sac-like ascus that contain 8 ascospores
Produced through 2 rounds of meiosis and 1 round of mitosis
These ascus burst open which release the ascospores into the air
For example, dead mans fingers grown out of wood
How do basidomycetes reproduce?
They for a specialised cell called a basidium
There are 4 basidiospores per basidium
Found in the gills of mushrooms
The basidiospores are released into the air on maturaiton
List the products of fungi
Toxins- Released a defence mechanism
Antibiotics
Penicillin
Cephalosporin
Mushrooms- Agaricus
Quorn- Fusarium
Citric acid- From Aspergillus
List the different type of toxins released by fungi
Mycotoxins; Ergot- produces Alkaloid toxin related to lysergic acid dimetylamide can cause paralysis
Aflatoxins; stored in foods and cause liver damage
Amaminta phalloides- ‘death cap fungus’, causes death
Psilocybin- found in magic mushroomed, psychedelic drugs
