Lecture 3

• Two types of fungi

  Yeast (unicellular)

  Mold (Multicellular)

  *some fungi can switch between being yeast or mold
• Characteristic of fungi

  has a membrane and membrane-bound organelle (like eukaryotic organisms) - rough endoplasmic reticulum, mitochondria, nucleus

  reproduces sexually (molds) and asexually (most yeasts and some molds) by budding
• Budding

  asexual way of reproduction, where new organisms are developed via already existing organism
• Yeasts?

  has colonies that look similar to bacterial colonies BUT are specifically not bacteria. over 1500 types of species in kingdom Fungi

  • special single EUKARYOTIC organisms
  • has more sophisticated cellular machinery (unlike a fairly basic cellular structure like bacteria)
• Fungal cell wall

  made up of ergosterol (like cholesterol and is a primary sterol)

  • the cell will die if there is no cell wall
  • no peptidoglycan layer
  • major structure is chitin
  • exploited for diagnosis
• Importance of fungal cell structures

  has ergosterol as primary sterol (sterol = nutrition yeasts need)

  • gives fungi specific shape
  • gives strength by protecting from organic solvents and UV nights
  • makes enzymes from walls (hydrolysis of sugars for nutrition)
• Fungal reproduction

  Spores: reproductive unit that is released into environment that will develop

  conidia: different type of spore
• Classification?

  gets hard due to so many types of size, shape, arrangment
• Medically relevant fungi (yeasts)


  candida spp. (around 200 total species)

  Cryptococcus spp.
• Medically relevant molds

  Dermatophytes (around 50 species)

  zygomocetes (normally does not cause infection but when it does, it is BAD)

  Hylaine molds (disease in immunocompromised people)

  Dimorphic fungi (6 spp.) mold in environment, yeast in humans
• Infection classification

  Superficial or cutaneous mycoses (skin level, hair, nails)

  Subcutaneous mycoses (deeper skin level, cuts, wounds)

  Systemic mycoses (blood)

  Opprtunistic mycoses
• How long does it take to identify?

  weeks

  Molds: 6 weeks

  Yeast: few days

  Bacteria: hours
• Candida spp.

  colonizes in normal flora of GI tract (often skin and environment)

  leads to infections in immunocompromised people

  can lead to a few infection aetiologies
• Cryptococcus spp.

  Most medically relevant species is cryptococcus neoformans and cryptococcus gattii.

  • does not normally cause infection but can lead to disease/infection in altered immune system people
  • found in soil and dried poop (bird or guano)
  • can lead to pneumonia, fundemis, meningitis
  • has large capsule around yeast cell that helps it evade immune system
• Dermatophytes

  direct group of fungi that only infect skin, hair and nail (but not systemic)

  • enzyme keratinase is made (helps breakdown of keratin found in hair, nails and skin)
  • has 3 genuses
  • trichophyton (hair, skin and nails)
  • microsporum (skin and hair)
  • epidermophyton (skin and nails)

  makes ringworm, athletes foot
• Dimorphic Fungi

  Can switch between being yeast and molds

  • histoplasmosis capsulatum (all around the world, not major pathogen)
  • blastomyces dermatiditis (North America, eastern USA)
  • Coccidoides immitis (in sand, texes, Nevada)
  • Paracoccidiodes brasilensis (south america)
  • sporthrix schleferi (gardening, soil, bud of rose bush)
  • Taloromyces marneffei (southeast asia)

  Temperature dependent (yeast = 37 degrees celsius, molds at 25 degrees)
• Opportiunistic mycoses

  fungi that are called "nonpathogenic" bus has the chance to cause illness in those with bad immune systems

  • in soil and envirionment
  • by molds can end with sinus infections, respiratory diseases and fungemia
  • Aspergillus is most common invasive mold (major cause of disease)

  aspergillus, fusarium
• Mucorales molds

  from BAD wound infections

  • fast growing fungi sorted by primitive coenocytic hyphae
  • environmental (soil, dung, vegetative matter)
  • rapid growth (lid lifters)
  • extremely aggressive and does not respect tissue planes)
• Lab detection of fungi

  gram stain and additional stain from specimens

  culture of specialized media (yeast: 1-3 days, dermatophytes up to 6 weeks, systemic 3-6 weeks)

  • multiple cam work better)
• Anti-fungal therapies

  try to attack fungi, but we need them to target business end (the cell wall) during synthesis