Exercise 2_ Morphology and Reproduction of Yeasts Flashcards
are fungi that exist predominantly or solely in a unicellular states.
Yeast
Yeats are found on
surfaces of the plant (abundant on the leaves, fruits and nectars of flowers surface (skin), mouth, gastrointestinal tract of animals, and insects
Few yeasts are pathogenic to
humans and warm-blooded animals
yeast are beneficial in several fermentation processes including
beer, bread and wine
Some yeasts are capable of forming
true mycelium and pseudomycelium
other terms for pseudomycelium
false mycelium or sprout mycelium
a mycelium-like structure consisting of chains of cells formed from sequential budding (sprouting)
pseudomycelium
Pseudomycelium can be demonstrated under what environmental condition
reduced oxygen conditions
is a vegetative structure that gives rise to arthrospore or blastospore in some species of yeasts
true mycelium
in yeast, true mycelium gives rise to
arthrospores and blastospores
is an asexual spore (conidium) formed from a pre-existing hypha
arthrospore
an asexual spore formed following the marked enlargement of a part of a cell before separation by a septum
blastospore
Asexual mode of reproduction in yeast
Budding, fission, as mycelia consisting of septate hyphae
an outgrowth develops from the parent cell and eventually separates as a daughter cell
budding
the parent cell simply divides and develop into two identical daughter cells
fission
sexual reproduction in yeasts
sexual spore formation
sexual spores of yeast
ascospore or basidiospore
yeast that are imperfect or lacks sexual phase
anamorphic
yeast cultures used in the exercise
Candida sp. Saccharomyces sp. Rhodotorula rubra Hansenula sp. Pichia sp.
Candida sp.
Budding (pseudomycelia) depending on the species (ascospore or other sexual phase
saccharomyces sp.
Budding (pseudomycelia) ascospores
Hansenula sp.
Budding Pseudomycelia Ascospores
Pichia sp.
Budding Pseudomycelia Ascospores
Rhodotorula rubra
Budding Pseudomycelia Basidiospores
What is the purpose of the cover slip in Dalmau plate?
It flattens the inoculum for better visualization, it also provides a partial anaerobic condition which encourages yeast to develop hyphae or mycelia or pseudomycelia (for those that cannot develop true mycelia) It also prevent contamination during microscopy
How is Schizosaccharomyces morphologically different from Saccharomyces?
Schizosaccharomyces are rod-shaped, divides asexually through fission, develops septa during cell division and develops true mycelia. Whereas, Saccharomyces are oval or round, divides asexually through budding, no septum formation, develops pseudomycelium.
Discuss PDA, MA, and AcA in studying yeast cultures.
PDA Potato provides essential nutrients which promotes fungal growth. Dextrose serves as a carbohydrate source for growth stimulants. Slightly acidic pH (~5.6) inhibits bacterial growth and promotes yeasts growth. AcA Sodium acetate as carbon source. Dextrose is the source of carbohydrates/energy. Yeast extract is nutritional resource (essential growth factors, amino acids and minerals) MA Malt extracts provide essential nutrients, amino acids, and vitamins necessary for fungal growth. Limited nitrogen content and carbon availability can induce sporulation in yeasts. Acidic pH inhibits bacterial growth and promote fungal growth.
PDA vs. AcA growth
Growth is faster in PDA as it provides more carbon source and other essential nutrients compared to AcA
Why is malachite green used in ascospore staining?
It is a small, basic (positively charged) dye It is stable under heat. Heat is required to destabilize proteins in the spore wall and allow entry of malachite green. Once it is trapped inside, it is retained strongly due to the tough and hydrophobic nature of the spore wall.
What is the significance of having asexual and sexual modes of reproduction?
Asexual reproduction can be more efficient in terms of energy and time as only one individual is required to produce an offspring, thus, can be used in rapid multiplication in stable environment. Sexual reproduction confers genetic diversity to the next generation necessary for adaptation.
What other characteristics should be used to accurately identify yeasts?
pathogenicity (virulence factors), Biochemical and physiological characteristics (enzyme activity, fermentation of sugar, pigment production, Molecular characterization (e.g., DNA sequencing, molecular markers)
