5) Saccharomyces Cerivisae Flashcards
what type of yeast is Sc?
budding
Can Sc be airborne?
no
it needs a vector to move
how many chromosomes does Sc have?
16
what is the Gay Lussac Equation?
180g sugar –> 92g ethanol + 88g CO2 (theoretical yield)
what are two forms that Sc can exist as?
haploid or diploid
what occurs to haploids and diploids when there are adequate nutrients present?
haploids and diploids both undergo repeated rounds of vegetative growth and mitosis
what happens to Sc when nutrients are depleted?
haploids and diploids arrest as SPC (stationary phase cells)
what are SPC? characteristics?
how are SPC different than proliferating/growing yeast cells
- SPC = stationary phase cells
- round and bright
- contains more storage CHO (trehalose and glycogen) than growing cells
- higher resistance to stresses than growing cells
what are the 2 mating types of haploid cells?
differentiate them.
what surface receptors do they have?
a: produces a pheromone “a factor”
alpha: produces “alpha factor”
each cell type has the surface receptor for the opposite mating type
what happens when the surface receptor on one of the mating haploid types is stimulated?
- cels stop in the G2 phase of the cell cycle
- cells stop proliferating and grow towards each oterh
- creates a “shmoo”
- once there is cell contact, they fuse together and form a diploid
diploid cells with no N will undergo ____ and ____.
what does this create?
meiosis and spore formulation, which results in 4 haploid spores contained in an ascus
what is an ascus? how does it compare to SPC?
- contains 4 haploid spores after sporulation
- has higher resistance to stresses than SPC
Sc vegetative proliferation occurs via _____
budding
what does the cell cycle have to control processes that occur?
checkpoint controls, where the cell cycle doesn’t continue if some processes haven’t happened (eg. mitosis won’t happen if DNA replication has not been completed)
what are 4 morphogenic aspects of the yeast cell cycle
- bud site selection: in rich media, haploids bud in an axial pattern, while diploids show polar budding
- polarity
- pattern
- rate of growth
how does growth occur in yeast?
building materials are packed into vesicles, docked at the plasma membrane, then incorporated into the growing cells
differentiate the products and substrates of growing and stationary phase
growing phase: Sc cells ferment glucose via glycolysis to form ethanol
stationary: Sc cells use ethanol already formed via TCA and glyoxylate cycles
why do Sc have specific transport proteins?
b/c most compounds needed for Sc metabolism can’t pass through phospholipid membranes, thus they must be transported through
describe the breakdown of maltose by Sc
- actively transported across the cell membrane
- hydrolyzed by alpha-glucosidase (aka maltase) to produce 2 glucose molecules
- glucose is broken down in glycolytic pathway
describe the breakdown of sucrose by Sc
sucrose is broken down to fructose + glucose (via invertase)
describe the cell walls of Sc
- cell walls have mechanical strength against physical damage
- has a homogenous inner layer (plasma membrane) and a fibrillary outer layer (implanted in inner layer and emanating from cell surface)
- composition: glucans, mannoproteins, chitin (most responsible for mechanical strength of cell wall)
what is around 50% composition of cell wall?
glucans
what are 2 types of amylases
- endoamylase: alpha amylase (breaks down alpha 1,4 links)
2. exoamylase: beta amylase (breaks down alpha 1,4 links) and gluco-amylase (Breaks down alpha 1,4 and alpha 1,3)
what is another name for oryzae
koji
what are main uses of oryzae/koji?
- east asian cuisine
- ferment soy beans, soy sauce, miso, breaks down rice starches into sugars for sake
what is oryzae
- fungus that secretes amylases that extracellularly degrades starches
how does A.oryzae form a hyphae
- asexually produces a conidium spore at the tip of a specialized hypha, capable of growing into a new multicellular organism
- if conditions are right, the conidium will swell and grow into a germ tube to form the hyphae
what is a hyphae?
individual secretions partitioned by septa
constitutes multicellular filamentous fungi
what is a hyphal tip
highly metabolically active
where growth of the fungi occurs from
how do A. oryzae cells communicate between each other?
how is this related to woronin bodies?
through the pore in the middle of septum
if cell damage is detected, woronin bodies will plug the pore to prevent danger to the entire organism
A. oryzae secretes amylases that do what?
extracellularly degrades starch
what is Spitzenkorper?
what does it do?
organelle present in the hyphal tip region; involved in accumulation and secretion of vesicles that contain secretory enzymes
- vesicle is then endocytosed right after fusion with cell membrane; then recycled for incorporation into new secretion vesicles. This is imp for sustaining high levels of amylases
what is a conidiophore? what is its mechanism?
- a special cell designed to produce conidium to spread the mold
- nutrients are passed from the hyphae into the budding conidia
- when conditions are right, the conidium prepares to germinate by swelling
- vacuoles involved in autophagy appear and grow to aid in the physical extrusion of cytoplasm at tips of the germ tubes
what is geotricum candidum?
rapid growing mold that prevents unwanted mold growth in moist cheeses
what is penicillium candidum
- produces fuzzy white mold on surface of bloomy rind cheeses
- includes Brie, Camembert, Coulommiers, French goat cheeses
- different strains can produce different flavours
what is penicillium roqueforti
- creates colored veins and surfaces
- major contributor to flavour in blue cheeses
describe why a symbiotic mix of MO is needed
- LAB usually needs nutrients that are provided by yeasts and molds
- difference in O2 requirements: molds and AAB are on the surface (aerobic) while LAB and yeasts are internal (anaerobic)
what are main ingredients in Sake?
H2O
rice
koji
yeast
what is the function of koji in sake?
what is aded after koji?
koji: converts starches in rice into sugars
LAB: colonizes sugars and grows for a second stage of fermentation, which kills wild yeast and prepares the solution for the fermentation by the brewing yeast
what is Fukuyama Pot vinegar?
traditional japanese rice vinegar
- rice + koji is added into a large pot and laid in an open air field
what rxns occur in the production of Fukuyama Pot vinegar?
- saccharification
- alcohol fermentation
- acetic acid fermentation
- lactic acid fermentation
what is milk kefir?
fermented beverage inoculated with kefir grains that harbor LAB, AAB, yeast and sometimes molds
what are characteristics of kefir grains?
- white, elastic, opaque, cauliflower shaped
- consists of water and water-insoluble kefiran (extracellular polysaccharide produced by LAB)
how are kefir cultures usually started?
via back slopping
what is kefiran? what are characteristics? describe composition.
- main EPS produced in kefir grains
- heteropolysaccharide
- composed by equal proportions of glucose and galactose
- mainly produced by Lactobacillus kefiranofaciens. But adding Saccharomyces sp. to the culture improves net quantity of kefiran
where are live kefir MO mostly found?
at exterior of kefir grains
