Mycology Unit Test 3

-over 1000 species
-unicellular
-multicellular forms have connected budding cells called pseudohyphae (false hyphae)
-ascomycota: saccharomycotina
-ascomycota: schizosaccharomycetes (fission yeasts)
-basidiomycota

Yeasts on:
-fruits, leaves, sap of plants
-skin/gut flora
-symbiosis with insects/plants

-chemoorganotrophs (use organic compounds as source of energy, do not require sunlight)
-obtain carbon from sugars (sucrose)
-anaerobic or use O2 for cellular respiration.

Budding- small portion of the cytoplasm in the parent cell becomes separated into a smaller daughter cell
-nucleus of mother cell splits, migrates to daughter cells
-daughter cell is conidium

-yeast will reproduce asexually when resources are limited
-most yeasts have two mating types: a and alpha
-plasmogamy & karyogamy fuse to form a diploid cell
-diploid cells then reproduce by budding
-a diploid cell will then become an ascus and enter meiosis to produce 4 haploid nuclei (spores)
-spores are released to become new haploid cells

-involves an equal division of the cytoplasm into 2 daughter cells
-fission yeast- includes S pombe, which is used in lab studies

S. cerevisiae
-baking- 4000 year old bakeries found in egypt
-fermenting alcoholic beverages (louis pasteur)
-model organism in cell biology (bio of eukaryotic cell and human biology)
-used to understand cell cycle, DNA rep, recombination, cell division, metabolism
-most important human proteins were first disc. in yeast as homologs (cell cycle proteins, signalling proteins...)
-first euk to have its genome sequenced for genome project

C. albicans
-aerial hyphae
-opportunistic pathogens
-infections in humans
-vaginal infections (candidasis) and mouth (thrush)
-yeasts sprout a hyphal outgrowth which penetrates membranes causing irritation and tissue shedding

Cryptococcus neoformans
-pathogen in immunocompromised individuals
-causes cryptococcosis (can be a fatal lung infection)

-produce spores that are forcibly discharged
-use clamp connections
-ex in Rhodoturula genus
-called red yeasts, as they contain carotenoids

-form invisible population on leaf surfaces
-dependent on material of leaf, and rain
-basidiospores shoot away from sterigmata
-if air has pollutants, the yeast will have less sporulation
-used to monitor short-term changes in air quality
-called a shadow, or mirror yeast

-staining with diazonium blue B
-basidiomycota will form red and violet pigments
-minimum, optimum, and max. temperature for growth/sporulation
-growth in presence of toxic compounds (sugar/salkt)
-cell morphology and method of conidiogenesis or sporulation

Fleischmann's yeast (1868)
-granulated S. cerevisiae active dry yeast that doesn't require fridge
-quality of yeast can be assessed by 'proofing'
-foams and produces bubbles

-baking yeast (s. cerevisiae) used as leavening agent
-yeast respire initially aerobically to convert the sugars present in dough into CO2
-causes dough to rise
-when O2 is depleted, anaerobic respiration produces ethanol as a waste product
-sourdough bread used flour and water instead of sugar
equation:

C6H12O6 ---> 2C2H5OH + 2CO2

-barley used to make brewers malt
-barley germinated, and then dried to arrest growth and may be roasted
-during growth, enzymes in barley are released to break down the membranes of starch cell walls, and convert insoluble starch to soluble starch
-barley malt screened, and crushed
-malt is mixed with hot water
-water/grain mix is MASH
-mash is heated, and enzymes in malt convert the cereal starches to fermentable and non-fermentable sugars

LAUTERING
-mash is transferred to a straining (lauter) vessel
-sugar in mash drains through the lauter and runs to the brew kettle (called WORT)
-wort boils in kettle while hops and other flavourings are added.
-during boiling in the brew kettle, large proteins in wort clump together
-the wort is transferred to a hot wort tank, where the raminaing solids from the hops and protein settle out and are removed
-wort is chilled and transferred to fermenting vessels
-yeast is added, and breaks down sugar in wort to CO2 and alcohol (3-12 days)
-2 yeast species of Saccharomyces are used
-top fermenting yeast brews lagers, and pilsner beers
-bottom fermenting yeast brews lagers and pilsner beer
-yeast is removed and beer is stored and packaged