Basics

Question 1

Characteristics of Fungi

Answer 1

Eukaryotic
Features: membrane bound nucleus, ER, mito, Golgi, lysosomes, linear chromosomes

Free (free living)-don’t need a specific host
Heterotrophic- nutrients come from organic Carbon and nitrogen
Saprobe/saprophyte: fungi that live off of dead material

Non motile

Question 2

Differences between Fungi and Higher Eukaryotic Cells

Answer 2

Fungal membranes have ergosterol (rather than cholesterol)

Anti fungal drug amphotericin B binds to ergosterol
Azoles and allylamine drugs interfere with ergosterol biosynthesis

Fungal cells have a rigid cell wall (made of carb polymers and proteins)
Carb polymers: chitin, alpha glucan, beta-glucan, alpha-mannon
Protein: mannoproteins
Echinocandins: drug that inhits beta-glucan synthase

Question 3

Fungal Morphologies

Answer 3

Yeast, Hyphae/Mycelium

Question 4

Yeast morphology

Answer 4

*Unicellular, spherical to ellipsoid
*Reproduce by budding or fission
*Some yeast elongate and adhere to one another forming pseudomycelium/pseudohyphae
*Pathogenic yeast:
Cryptococcus neoformans (exist only as yeast)
Histoplasma capsulatum is dimorphic

Question 5

Hyphae/Mycelium (mold)

Answer 5

Branching tubules
3 kinds:
-Non septate (coenocytic)
-Septate Uninucleate
-Septate Multinucleate

Mycelium is a mass of intertwined hyphae that accumulate during active growth

Pathogenic mold:
Aspergillus exist only as mold
Rhizoids (root like structures)

Question 6

General Life Cycle of Fungi

Answer 6

Asexual spores will germinate in the correct conditions, then under certain conditions they will become hyphus (haploid) of either (male/female or +/-), then under certain conditons they will find a mate and create a zygote (2n), that can undergo meiosis and make haploid sexual spores.

Spores are the same thing: they are haploid cells coming from a fungi: if its a sexual spore it comes from a zygote that was 2n and underwent meiosis, if its a asexual spore, it burst out of hyphae that was 1n thru budding or fisssion

Question 7

A sexual reproductive elements

Answer 7

*Blastoconidia (outcome of budding)
if it happens lots it will form a pseudohyphae
*Chlamydoconidia- thick cell walled single cells resistent to adverse conditions
*Arthroconidia- single celled conidia that break off of hyphal cells

*Conidiospores- born naked leaves macroconidia (large multi cells), and microconidia (small, single celled)

Asexual spores: Sporangiospores- single celled spores formed in sacs called sporangia at the end of a hyphae
Sac of balls of spores

Question 8

Fungal toxins

Answer 8

• Mycotoxins (Mycotoxicoses)- are poisonous secondary metabolites from fungi they come from contaminated food
• ingestion of mushrooms- liver and kidney damage alpha-amanitin
• aflatoxin-most carcinogenic
• ergot alkaloids-gangrene, nervous spasms, psychotic dilusions, muscle contractions, blood vessel
• mycotoxins addtl: citrinin, fumonisins, ochratoxin, trichothecenes

Question 9

Diagnostic Lab procedures

Answer 9

• Direct microscopic examination- KOH technique
• Cultivation on blood agar at 37 C, Sabouraud’s agar and on other special culture media.
• Microscopic examination of structure of fungus
• Serology
• PCR
• FISH
• Mass Spec

Question 10

Resistance to Antifungal Drugs

Answer 10

• Fungi dont destroy or modify Antifungal drugs
• Resistance occurs thru efflux pumps, target alterations, and reduced access to drug targets
• Antifungal resistance genes are not transferred from cell to cell
• Primary Resistance- an organism that resistant w/o prior exposure to the drug
• Secondary Resistance- an organism that develops resistance after exposure
• Eagle effect is emerging w/ fungi- resistance to high concentrations, not resistance to low concentrations