Mycology

Question 1

Fungal relationships

Answer 1

Saprobes: organism that lives on dead or decaying material
Commensals: organism that lives with another organism deriving benefits from host, may or may not be beneficial, NOT harmed
Parasites: benefits from the host without contributing to the relationship and is harmful to host

Question 2

Plasmalemma

Answer 2

Bilayered of phospholipids and sterols (ergosterol, zymosterol)

Protects cytoplasmic contents, regulates intake and secretion of solutes, facilitates capsule and cell wall synthesis

Question 3

Ergosterol

Answer 3

Pharmacological target
Imidazole antifungals inhibit synthesis (more specific)
Polyene antifungals bind more tightly to ergosterol than cholesterol but created more side effects

Question 4

Cell wall

Answer 4

Antigenic in nature
Multilayered: polysaccharides (hexose and hexosamine polymers) 90% and proteins and glycoproteins 10%

Provides shape, rigidity, strength, and protection from osmotic shock

Question 5

Major polysaccharides of fungal cell wall

Answer 5

Chitin (N-acetyl glucosamine)
Alpha-glucan (D-glucose)
Beta-glucan (D-glucose)
Mann an (D-mannose)

Question 6

Capsule

Answer 6

Polysaccharide structure
Antiohagocytic and virulence factor
Not all fungi

Cryptococcus neoformans

Question 7

Yeast

Answer 7

Unicellular
Reproduce by nuclear fission or budding
Bud = blastoconidia
Pseudohyphae

Question 8

Mold

Answer 8

Multicellular
Hyphae (mycelium)
Spores

Question 9

Hyphae

Answer 9

Septate: divided by crosswalls

Coenocytic or nonseptate: multinucleate

Question 10

Mycelium

Answer 10

Project above surface (aerial)

Vegetative: growth on or beneath surface

Question 11

Dimorphic

Answer 11

Capable of growing in mold or yeast form under different environmental conditions (temp, CO2, nutrients)

Thermal dimorphism
<37C grows as filamentous fungi (mold)
>37C grows as yeast

Question 12

Fungal spores

Answer 12

Reproduction: normally haploid, unicellular

Sexual reproduction: involves meiosis, preceded by fusion of protoplasm and nuclei of two compatible mating types, telomorph

Asexual reproduction: involves mitosis, anamorph

Question 13

Laboratory diagnosis

Answer 13

Direct microscopic examination
Potassium hydroxide - colorless cells
Calcofluor white - fluorescence
India ink evaluation of CSF - colorless cells with halos (Cryptococcus neoformans)

Culture (slow growing)
Sabouraud dextrose agar on mycobiotic agar
Morphology or PCR

Serology (Ab screening)

Molecular techniques (fungal antigen detection)