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Blueboom/Fungi

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Fungi

  • Eukaryotic: nucleus / nuclear membrane but no chorophyll
  • macroforms mushrooms puffballs gill fungi
  • microforms molds & yeasts
  • all fungi are saprobes(live on dead/decaying matter)
  • types of relationships
    • symbionts mutal advantage
    • commensals one benefits orther is neither harmed/hurt
    • parasites one benefits and is harmful to the host

Micro fungi

  • Yeasts unicellular
  • typically round/oval single cells
  • 4-5 micrometers in diameter up to 24 micrometers
  • reproduce asexually by budding
  • form elongated tubes termed pseudohypae

Molds

  • multucellular
  • long filamentous/tubular structures hyphae which intertwine to form the mycelium
  • hypha range from 5-50 micrometers in length 2-4 micro in diameter
  • reproduce sexually and/or asexual by producing spores

Hyphae

  • thread like branching filaments nucleated tubes of cytoplasm
  • characterised by presence/absense of wall partitions
  • septate partitioned by cross walls
  • aseptate or coenocytic not partitioned
  • differences between hyphae vs yeast pseudohyphae

feature present in permanent hyphae differentiation hyphae branching true hyphae arthrospores and chlamydospores true hyphae

Mycelium

  • intertwined mat of hyphae
  • composed of 2 portions
  • vegatative- attached to substrate penetrates to obtain substrate
  • reporductive represented by aerial structures
  • asexual reproduction propagules (conidia) (spores)

Dimorphic fungi

  • yeast<->mold
  • morphological and physiological conversion of certan fungi from one phenotype to another
  • same organism can exhibit 2 different forms
  • depends on chemical and physical factors
  • important pathogenically
  • candida albicans coccidio immitis, histoplasma cap........lots


  • what are the dimorphic forms
  • freeliving state mycelial or hyphal forms
  • occurs at sub physiological temperature distinct sexual forms are displayed
  • parasitic yeast forms
  • due mainly to physiological temperature 37 oval morphology
  • most but not all fungi are dimorphic
  • aspergillus species are always in mycelial phase even in deep tissue infections
  • torula species exist only as yeast
  • candida albicans is truly dimrphic yeast human tissue
  • mycelial (mold) form in culture
  • produces pseudohypae in biofilm superficial, cutaneous and mucus membrane infections

Fungal cultivation

  • Isolate using Sabouraud's agar
    • Made from protein hydrolysate and agar
    • Low pH (5.6) to inhibit the faster growing bacteria

Fungal staining procedures

  • KOH preparation/procedure
  1. take scraping from margin (not center) of lesion
  2. place on clean slide
  3. add 2-4 drops of 10% KOH in water
  4. warm slide do not boil -> allows kOH to denature eukaryotic tissue
  5. optionally add 1 drop of lactophenol cotton blue
  6. add cover slip
  7. examine immediately under high dry magnification

Use of staining

  • determine fungal morphology ie yeast or mould
  • if mold identify hyphae septate/nonseptate spores (thallospores or sporangium) (type of arrangement)

Fungi stain gram positive, can differentiate by size ....fungi are HUGE

Fungal architecture

  • eukaryotic
    • cell surface - glycocalyx (there's a capsule in 1 species)
    • cell wall
    • cytoplasmic membrane
    • nucleus - nuclear envelope nucleolus chromosome
    • cytoplasm organelle er golgi mitochondria vaculoes
    • cytoskeleton microtubules microfilaments
    • ribosomes 80s
  • absence of locomotion structures ( no flagella)

*absense of capsules except cryptococcus neoformans************

Cell Wall

  • contains no peptidoglycan layer ***differs from bacteria
  • thick and rigid complex composition
  • chitin (polymer of nacetylDglucosamine) (not NAG molecule)
  • additional polysacc such as glucans and mannan
  • proteins
  • may contain lipids

Cytoplasmic Membrane

  • typical phospholipid bilayer but differs from bacteria
  • contains sterols ergosterol but not cholesterol
  • site of antifungal drugs
  • functions the same as all membranes

Cytoplasmic Contents

  • differs from bacteria
  • more complex
  • golgi body, endoplamsic reticulum cytoskeleton
  • ribosome 80S
  • microtubles spindle fibers.. tubulin - site of antifungal drug

Nucleus (euk)

  • differs from bacteria
  • nuclear membrane bound (nuclear envelope)
  • most haploid
  • contains the chromosome larger than bacteria

Fungal classification

  • kingdom: fungi
  • 2 divisions
  • myxomycota eumycota 5 subdivisions 4 are pathogenic to humans
  • class zygomycetes most primitive filamentous non-septate separates them from other subdivisions
  • reproduce sexually zygospores and asexually sporangiospores
  • not primary pathogens (opportunistic)
  • rhizopus mucor water molds

Class Ascomycetes

  • septate produce sexual ascospores and asexual conidia spores
  • members include yeasts and molds - dermatophytes (skin infections ) some aspergillus species

Class Basidomycetes

  • septate produce sexual spores basidospores
  • members include mushrooms and puffballs
  • only human pathogen filobasidella neoforms (sexually reproductive form of C. neoformans)

Class Deuteromycetes

  • septate: reproduce asexually septate hyphae sexual reprodutive structures unknown
  • includes yeasts and molds
  • ie candida coccidioides species
  • epidermophyton species
  • malassezia
  • microsporium species
  • trichophyton speicies

Class Archiascomycetes

  • reproduce sexually fusion and asexually binary fission
  • only member pneumocystis jirovecii (previously known as P. Carnii)
  • Fungal disease mycoses
  • systemic by inhalation initially pulmonary---> disseminated
  • subcutaneous infections of deep layers (muscle and fascia) most by wound puncture remain localized
  • cutaneous invade keratinized and cutaneous tissue also hair shaft and nail bed
  • superficial infections of limited to surfaces of skin and hair innocuous and reappear (also nails) (rarley evoke an immune response
  • opportunistic infections debilitated and traumatized patients, immuno-suppressed
  • mycotoxins: mycetismus (amantia mushroom) afloatoxin (aspergillus flavus)

Features shared with bacteria

  1. microorganisms
  2. all fungi grow axenically without others on artifical media
  3. all fungi are aerobic or facultative
  4. most fungi are not capable of invading living human tissue

Fungal features different from bacteria

  1. all fungi are eukaryotic
  2. different internal organelles
  3. membrane bound nuc, chromosomes that sort by mitosis
  4. 80s ribosomes
  5. larger than bacteria
  6. biochemically different
  7. fungi grow more slowly
  8. fungi have multiple reproductive patterns usually but not always


Unique features of fungi

  • Eukaryotes
  • Biphasic reproduction
  • Chitin Cell wall (homo-poly-N-Acetylglucosamine)
    • has glucans
    • Peptidomannans instead of LPS which can be used for serological dx
    • not disolved in KOH - useful for dx
  • Most are strict aerobes
  • Heterotrophic, non photosynthetic and saprophytic

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