(O) 31: Mycology I Flashcards
Mycology
The study of fungus
fungi are all EUKARYOTIC organisms
Are fungi closer to humans or plants?
Fungi ate closer to humans than plants
Most fungi are obligate aerobes (like humans)
- take in oxygen and respire CO2
Amillaria
one of largest fungi in the world
Plant cell vs fungal cell
Plant
- have cell wall made of cellulose
- have one nucleus per cell
- autotrophs (make their own energy)
- membranes have phytosterols
- store food as STARCH in granules
Fungus
- have cell wall made of CHITIN (crunchy exterior, more rigid than cellulose)
- may be uninucleated or multinucleated
- heterotrophs (need energy from env)
- membranes have ergosterol
- store food as GLYCOGEN in granules
Classification of Fungi
- spore formation
- fungal genomics
- modes of nutrition (saprophytic, parasitic, symbiotic)
Mode of Nutrition
Saprophytic
fungi obtain their nutrition by feeding on DEAD ORGANIC substances
Mode of Nutrition
Parasitic
fungi obtain nutrition by living on other LIVING ORGANISMS and absorb nutrients from their host
Mode of Nutrition
Symbiotic
fungi live by having an INTERDEPENDENT relationship w/ other species in which BOTH are mutually benefited
ex. lichens (algae), mycorrhiza (plants)
Fungal Morophology
- Filamentous fungi
- macrofungi (ex. mushroom)
- microfungi (mold) - Yeast
- microfungi
Filamentous fungi
- fungi grow as filaments called HYPHAE (extend only at extreme tips)
- fungi exhibit APICAL GROWTH in contrast to may other filamentous organisms
- fungal hyphae branch repeatedly to make a network called a MYCELIUM
Yeast
- 1% of fungi grow as single-celled yeasts (ex. Saccharomyces cerevisiae)
- some species are dimorphic and can switch btwn yeast + hyphal (filamentous) phase in response to environmental conditions (pseudohyphae)
Fungal Reproduction
- asexual
- sexual
- parasexual
Asexual fungal reproduction
- most COMMON mode
- asexually reproducing fungi are called ANAMORPHS
- asexual propagules are called SPORES/CONIDIA produced after mitosis
Sexual fungal reproduction
- sexually reproducing fungu are called TELEOMORPHS
- sexual propagules are produced by fusion of 2 nuclei that then undergo meiosis
Parasexual fungal reproduction
involves genetic recombination without requirement of specific sexual structures
Saccharomyces cerevisiae life cycle
Yeast
- Asexual reproduction (mitosis) w/ an “a” and an “alpha” cell
- undergoes budding - Sexual reproduction
- budding yeast becomes Schmoo cells which then differentiate into zygote
- zygote then buds and splits into diploids (alpha and “a”)
- ascus formaton meiosis (2 alpha and 2 “a” cells)
Aspergillus Nidulans life cycle
Filamentous fungi
Sexual + asexual + parasexual cycles
Asexual
- conidium (seed/spore) lands in soil + germinates to form hyphae
- conidiophores form = more conidia form
Sexual
- 2 nuclei from conidium fuse via meiosis (diploid –> 4 –> 8) to form ascopore
- can do SELF sexual fertilization to make fruiting bodies with ascospores which make hyphae
Parasexual (unstable, no meiosis)
- hyphal fusion to make heterodikaryon
- heterodikaryon undergoes nuclear fusion to make DILPOID HYPHAE (2n)
- chromosome loss to make haploid again
Sporulation
Biological
- dissemination of spores
- reproduction
- allow fungus to move to new food source (or find more suitable env)
- allows fungus to survive periods of adversity
- introduce new genetic combinations into a population
Practical
- rapid identification (classification)
- source of inocula for human infection and contamination
Fungi: friend or foe?
Mostly friendly
3% of known mushroom varieties are poisonous to humans
Benefits of fungi
- nutrient cycling (frees up nutrients for plants b/c they are decomposers, makes N available + mobilizes Phos.)
- carbon cycling + climate regulation
- nutrition and food security
- human health
- environmental protection (used to clean up oil spills + get rid of plastics)
- sustainable materials (mycelium can be used for fabrics)
Fungi as food
- mushrooms have been used for food, medicinal purposes as hallucinogenic agents in rituals, or to start a fire for centuries
Asia is biggest producer of mushrooms + truffles
Fungiculture and nutrition
- mushrooms are nutritionally LOW IN ENERGY content
- rich in dietary fibre from vitamin B
- mushrooms collected outdoors are rich in vitamin D (can also become rich in vitamin D by treatment w/ UV light)
We usually harvest fruitbody
Yeast in food production
For
- baking
- making alcohol beverages
Yeast fermentation = releases CO2 + produces ethanol
Yeast and baking
Most common yeast in breadmaking is SACCHAROMYCES CEREVISIAE
- feeds on sugars in bread dough and produces CO2 gas
- forms bubbles in dough = expands
- sugar and eggs SPEED up fermentation
- fats and salt SLOW fermentation down
- ethanol is evaporated when bread bakes
Yeast and brewing
- yeasts ferment the sugars present in malted barley to produce alcohol
- Saccharomyces cerevisiae is used to make ALE-type beers aka TOP-fermenting yeast
- bottom-fermenting yeasts like Saccharomyces pastorianus are used to make LAGERS
- ethanol tolerance of yeast ranges from 5-21% depending on yeast strain and conditions of env. (yeast self limits)
Yeast and wine-making
- alcohol in wine is formed by fermentation of sugars in grape juice w/ CO2 as a byproduct
- Saccharomyces cerevisiae is added to ensure fermentation is reliable
- sparkling wine is made by adding yeast to wine when it is BOTTLED (CO2 formed in second fermentation is trapped as bubbles)
Cheese
Filamentous fungi are important in manufacturing and ripening of:
- blue-veined cheeses
- soft-ripened cheeses (Brie, Camembert)
some cheeses have mold introduced to create a protective rind
- others are spiked w/ stainless steel rods to infuse model deep into the cheese
Quorn
- mycoprotein developed due to prediction of protein-rch food shortage in 1960s
- produced from cultures of fungus FUSARIUM VENENATUM (filamentous fungus)
- sold both as a cooking ingredient + as a meat substitute
Quorn Production
- fermentation - to grow organism
- RNA reduction
- Centrifuge - separate solids + liquids
- Chiller - harvest mycoprotein paste
- Despatch
