week 6 - fungi Flashcards
fungi key features:
fungal cell
- Typical eukaryotic cell structure
- Except:
o Ergosterol instead of cholesterol in plasma membrane (also in some protists)
fungi key features:
flagellated?
- Very rarely flagellated
o So often not motile
fungi key features:
cell wall
o Chitin
o Long chain polymer of N-acetylglucosamine
o Produced by chitin synthase (usually multiple paralogues in a genome)
characteristics of the fungal kingdom
- A monophyletic group
- One common ancestor
- 100,000 species known, total probably >1.5 million
o Likely millions of species we are unaware of
characteristics of the fungal kingdom:
chemoogranotrophs
o All derive energy by the breakdown of organic materia
o Same as us (not like plants)
o Do most of the digestion on the outside
Secrete enzyme
Then stuff wanted seeps through pores
characteristics of the fungal kingdom:
important as..
o Decomposers
Have liganases (breaks down ligan in plants)
Symbiosis – plant life into land (nutrients in soils), interaction and collaboration
o Food and drink industry
o Disease agents (esp. crops)
fungal lifestyles
- Always yeast (Saccharomyces cerevisiae)
- Always hyphal (Agaricus bispora)
o Type of growth: Hyphal tip growth is characterized by the initial establishment of one growth site, which is followed by its continuous maintenance.
o A hypha is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium - A mixture (Candida albicans) = dimorphic
- Reproduction is often asexual
o Hyphal spread
o Single cell budding – e.g. yeast
o Asexual spores
filamentous fungi
- Filamentous Fungal morphologies
o Moulds
o Mushrooms - Fruiting body for spore production
o When conditions are right
filamentous fungi
- growth
- Spore to hyphae = GERMINATION
- GERM TUBE = first hyphae to emerge from a spore
- Some spores have a predefined point for germination = GERM PORE
o Where cell wall is weaker (on purpose) - Some swell before germ tube emerges
- Environmental stimuli needed to initiate
o In favourable conditions spores germinate (humidity, temp, etc)
o Get swelling
o Then one single new hyphae
o Which keeps growing to make a mass of hyphae
o Spores are a vehicle for transmission into new environments
filamentous fungi
consists of:
- Consist of long filaments of cells joint end to end = hyphae
filamentous fungi:
main structure:
Hyphae – rigid tubes containing cytoplasm
o Interconnected compartments, not individual cells
o Interconnected by septum
Extension of cell wall to add structure of hyphae
filamentous fungi:
growth
Filamentous fungi – growth
- Hyphae typically grow by apical growth:
o Extension at the tip
o New cells made at the front
o This is how it grows
New cells being formed at tip
In order to extent
Clustered area at tip of hyphae
Macrovesicles (glucan) with micro vesicles (chitin) inside
tropisms
- Hyphal tips show tropism to a variety of substances
o Nutrients
o Amino acids
o Volatile metabolites
o Sex pheromones
o light
Filamentous fungi
– four types of fungal hyphae
- Septate or Coenocytic
- Vegetative or Arial
Filamentous fungi
separate hyphae
- Joint cells have distinct separations called septa, contain pores
o more typical model
Filamentous fungi
coenocytic hyphae:
- Hyphae consists of fused cells, multinucleated
o More prominent in the older groups of fungi
o No distinct markers between cells
o (any negative mutations in one nuclei very easily compensated more, lots of nucelli as no proper separation)
Filamentous Fungi
– Septa
functions
o Structural support
o Allow movement of cell content between cells
Whole organells (depends on species)
o Damage protection
- Made of similar things as the cell wall
- Structure and control varies between fungal species
Filamentous fungi – Growth
- Mass of hyphae = mycelium (pural: mucelia)
Filamentous fungi – Growth
vegetative hyphae
- Grow along the surface
o Sectreting enzymes and absorbing material - Obtain nutrients filamentous = max surface area
Filamentous fungi – Growth
Aerial hyphae
- Stick up from the mycelium
o Up and out of the nutrient
Main purpose of spore production
Into new environment - Spores for reproduction
YEASTS
- Non-filamentous, unicellular, oval
- Facultative anaerobes
o Ferment carbohydrates into alcohol and carbon in absence of oxygen
YEAST
two types
budding
fission
BUDDING YEAST
- Divide by producing outgrowth called a bud
- Bud enlarges and seperates from mother cell
o With a septin ring
The pinching off is drivien by spetin
Septin ring forms and then it closes causing daughter cell to pinch off (alike actin and microtubules) - Asymmetric division
- Example: Saccharomyces cerevisiae, Cryptococcus neoformans, Candida glabrata, Malassezia furfur
FISSION YEAST
- Division by elongation of mother cell and mitosis
- Daughter cells separate by formation of septa in the centre
o Actin rings
o Actin ring closes off and separate cells (quick snap) - Example: Schizosaccharomyces pombe
DIMORPHIC FUNGI
- Grow as multicellular hyphae OR unicellular yeast
o Depending on environmental conditions
Dimorphism
- Some pathogens of humans exhibit dimorphism
- Plays an important role in how and why they cause disease
Dimorphism and disease
Candida albicans:
environmental change becomes a hyphae: now causes a problem
Histoplasma capsulatum:
budding form causes a switch to a pathogen
fungi summary:
fungal morphologies
o Yeast, filamentous and dimorphic
fungi summary:
fungal growth patterns
o Germination of spores
o Apical growth of hyphae
o Septate vs coenocytic
o Budding vs fission
fungi summary:
the fungal phyla
o Determined by spore containing structures
THE FUNGAL PHYLA
- Characterised by the structure of the spore containing organ
THE FUNGAL PHYLA:
Chytridiomycota
- Most primitive fungi
- Approx. 1000 species
- Many chytrids are aquatic
- Motile
o Zoospores in Zoosporangium - Chytridiomycosis
o Batrachochytrium dendrobatids
THE FUNGAL PHYLA:
Mucormycota
- Approx.. 1000 species
- Coenocytic hyphae
- Food spoilage
- Mucormycosis
have zygosporangium with zygospores inside
THE FUNGAL PHYLA:
Glomeromycota
- Approx. 230 species
- Arbuscular mycorrhizas (>80% plants)
- Coenocytic hyphae
- Fungus helps plant to capture nutrients such as:
o phosphorus, sulphur and nitrogen - Plant provides carbohydrates
- Obligate plant symbionts
e.g. Glomus mosseae
- Sexual lifecycle unknown
o Form Glomersopores from hyphae tips
THE FUNGAL PHYLA:
Ascomycota
- Approx. 65, 000 species
- Can form ascocarp fruiting body septate hyphae
- Example: Morchella, Gailella
- Asexual = conidia on a conidiophore
Sexual = Ascus containing ascospores
THE FUNGAL PHYLA
Ascomycota
good
o Saccharmyces cerevisiae
o Saccharomyces carlsberensis
o Penicillum roqueforti
o Pencillium chrusogenum
THE FUNGAL PHYLA
Ascomycota
bad (cause disease)
o Candida albicans
o Asperguillus fumigatus
o Histoplasma capsulatum
o Coccidioides immitis
o Magnaporthe oryzae
o Truchophyton rubrum
o Malassezia glabosa
THE FUNGAL PHYLA
Basidiomycota
- > 30,000 species
- Basidium with basidiospores
- Can form basiocarp (fruiting body) = MUSHROOM
- Mycorrhizal fungi too
Mantle = think layer of fungal cells grows to tip of roots
Hartig net = fungal cells growing between epidermis cells
About 2% of plant species
- Examples:
o Amanita muscaria, Amanita phalloides, Coprinopsis atramentaria (all mushrooms
o Cryptococcus neoformans
fungal morphology and growth:
the structure of fungal cells
o Nucleus
o Membrane
o Chitosomes
o Cell wall
fungal morphology and growth:
the fungal nucleus
- Ploidy
- Most haploid with 6-20 chromosomes
- Others alternate between haploid and diploid
- Unique features of fungal nuclei:
o Membrane remains intact during mitosis
o No clear metaphase plate
fungal morphology and growth:
fungal cytoplasmic organelles
- Plasma membrane
o Phospholipid bilayer
Anchorage for enzymes/proteins such as chitin synthases or glucan synthases
Contains ergosterol - Chitosomes
o Microvesicle for chitin synthesis
fungal morphology and growth:
fungal cell wall
- Structural barrier
- Environmental interface
o Protects against osmotic lysis
o Contain pigments for protection
o Mediates interaction with other organisms
