Lab 7

Question 1

Know the differences between fungi and bacteria

Answer 1

Bacteria: smaller, prokaryotic, cause more infections and do not require immunocompromised host, reproduce asexually
Fungi: larger, eukaryotic, morphology is more diverse and sophisticated, cause much fewer infections but often require an immunocompromised host, reproduce sexually or asexually

Question 2

Know which type of patient can be infected by fungal diseases

Answer 2

Often requires an immunocompromised host

Question 3

Know the different stages of the fungal life cycle

Answer 3

Fungi start their life cycle as spores. Spores can be single cells or more complex structures and are a product of asexual reproduction. Once the fungus is mature, sporulating structures will begin to form. These structures differ from species to species

Spores –> Germination –> Hyphae branching –> Mycelium –> Sporulation

Question 4

Understand the differences between septate and aseptate hyphae, and how to visually distinguish them

Answer 4

Aseptate hyphae are a long, continuous tube of cytoplasm. Septate hyphae look like multiple cells (but are actually one long, continuous tube of cytoplasm)

Question 5

Know how to culture a fungal mold in a lab setting

Answer 5

To culture you cut a small square out of a culture plate using a sterile scalpel and place the square onto the media

Question 6

Know which dye was used to stain culture slides

Answer 6

Lactophenol blue

Question 7

Know which components of a mold stain we use to identify it

Answer 7

Molds have hyphae and sporulating structures when mature while yeast have pseudohyphae or a capsule depending on species

Question 8

Know which media we used for mold culturing and why we used it

Answer 8

Sabouraud’s agar - typical growth media
Minimal medium - low nutrient media, stresses mold
BHI - high nutrient media
PDA - encourages sporulation
Malt agar - reflects phenotypic activity
Glass plate - slide culture

Question 9

Know what differentiates a mold from a yeast

Answer 9

Molds have hyphae while yeast have pseudohyphae or a capsule depending on species. Yeasts are macroscopically similar to each other while molds are macroscopically different from one another

Question 10

Know the difference between pseudohyphae and hyphae

Answer 10

Pseudohyphae: do not have septa, single nucleus, think of them as individual cells
Hyphae: septa presence depends on the species, are multinucleated, think of them as continuous tube of cytoplasm

Question 11

Know what a capsule is, what it’s made of, and what it does for a yeast cell

Answer 11

A capsule is a layer that surrounds the microbe’s outer envelope. It is made of exopolysaccharides. It protects the yeast from the host’s immune system

Question 12

Know which dyes were used to identify pseudohyphae, and which was used to identify capsules

Answer 12

Pseudohyphae: lactophenol blue
Capsule: India ink

Question 13

Know which media we used for yeast culturing and why we used it

Answer 13

Inoculate in the dark:
- Chromagar: changes color depending on species present
- Caffeic acid agar: stimulates melanin production in C. neoformans
Inoculate in the light:
- Thioglycolate broth: causes anaerobic stress, simulating pseudohyphae production
- BHI + serum slant: contains blood serum, stimulates virulence factors (pseudohyphae, capsules)
- Yeast-malt agar: one at room temp and one at 37°C
- Cornmeal + Tween agar (blue color): inoculate anaerobically to look for pseudohyphae production
- Fermentation tubes (maltose, sucrose, galactose): determine sugar fermentation
- Urease plate: tests if the organism produces urease enzyme

(These media are used to stimulate environments that can stress or trick your yeasts that can showcase their unique structures)