Microbiology - 4 - Fungi

Question 1

What are the structures of a fungal cell?

Answer 1

Basics:

• decomposers in the energy cycle
• becoming increasingly common, esp immunocompromised patients
• EUK w/ higher complexity than bacteria
  
  • acquire nutrients from external environment
• Disease = mycoses
  
  • often relapse over time
  • acute disease = uncommon w/ fungal infections

Stucture:

• spore-bearing
• reproduce sexually & asexually
• can be unicellular or multicellular

Question 2

How do fungi differ from other EUK cells?

Answer 2

Cell wall

• rigid & external to cytoplasmic membrane

Sterole make-up

• cytoplasmic membrane
• dominant = ergosterol (humans = cholesterol)

Fungi have complex polysaccharides:

• mannans, glucans, chitins

Question 3

What is fungal metabolism?

Answer 3

Difference btw fungi & plants:

• fungi must acquire nutrients from EXOGENOUS SOURCE

Metabolism:

• most grow w/ simle carbon & nitrogen sources
  
  • often from decaying matter
• most = strict aerobes
  
  • some can be anaerobic

Question 4

What is an example of fungal dimorphism? How does it impact pathogenesis for human infection?

Answer 4

Fungal dimorphism:

• can grow as yeasts or molds
  
  • allows them to adapt to new environments

Thermally dimorphic

• shift based on temp
• yeast grow @ 37 deg (in humans)
• mold grow in minimal nutrient / temp

Question 5

What are the 3 major classifications of fungal infections (mycoses)?

Answer 5

1. Morphology & growth forms
2. Severity of infection
3. Opportunistic vs. true pathogen

1. Superficial mycoses
   
   • grows on body surface (skin, hair, nail, mouth, vagina)
     
     • ex: vaginal candidiasis (mostly molds)
   • person-to-person contact or from animal contact
2. Subcutaneous mycoses
   
   • nails/deeper layers of skin
     
     • ex: madura foot/sporotrichosis (molds)
   • infect following skin penetration
3. Systemic or deep mycoses
   
   • involves internal organs
     
     • ex: histoplasmosis; systemic candidiasis (mostly yeast)
   • affect healthy peeps/opportunistic infection in compromised peeps
   • via respiratory or IV lines

Notes:

• Neutriphils help control invasion