Mycology: Introduction Flashcards
What are fungi?
eukaryotic, non-photosynthetic heterotrophs that produce exoenzymes and obtain nutrients by absorption
What are the 2 forms fungi take based on their sexual reproductive life cycle? What kind or reproduction is spore formation?
- TELEMORPH = sexual form
- ANAMORPH = asexual form
can be sexual or asexual
What are mitosporic fungi? In what 3 ways are fungi characterized based on how they get nutrients?
fungi that lack meiotic stages
- saprophytic**
- parasitic
- mutualistic
What are the cell walls of fungi made out of?
chitin
How do most fungi grow on media? What 2 things are they able to tolerate? What media is most commonly used?
grow aerobically at 25 degrees C
- high osmotic pressure
- low pH
Saubouraund dextrose agar at 27-37 degrees C
What 3 phyla of fungi are of veterinary importance?
- Ascomycota
- Basidiomycota
- Zygomycota`
What are the 2 main morphological fungi?
- molds - branching filaments (hyphae)
- yeasts - unicellular, oval, spherical
dimorphic can occur as both
What does Candida albicans have a unique structure?
pleoorphic - produces other forms in addition to molds and yeast
What are the major components of hyphal cell walls? Yeast?
MOLD/HYPHAE: carbohydrate components including chitin macromolecules with cellulose cross-linkages
YEAST: protein complexed with polysaccharides and a range of lipids (if bilayered, it also contains cholesterol)
What are present in both molds and yeasts?
- nuclei with well-defined nuclear membranes
- mitochondria
- networks of microtubules
What are the 3 types of hyphae?
- separated hyphae
- aseptate hyphae
- vegetative and aerial hyphae
How do fungi grow? What leads to spore-bearing structures?
- spore
- hyphae
- mycelium (anchors into medium)
hyphae elongated into aerial hyphae and give off spore-bearing structures
How do most yeasts asexually reproduce?
budding
Basal fungal structures:
What are the 7 types of asexual spores produced by fungi of veterinary importance?
- ARTHROCONIDIA: spores formed and subsequently released during hyphal fragmentation, either successively or with intervening cells (fragmentation)
- BLASTOCONIDIA: conidia are produced by budding from a mother cell, from hyphae, or from pseudohyphae
- CHLAMYDOCONIDIA: thick-walled, resistant spores with storage products, commonly formed in unfavorable conditions
- MACROCONIDIA: large, multi-celled conidia produced by dermatophytes in culture
- MICROCONIDIA: small conidia produced by some dermatophytes
- PHIALOCONIDIA: conidia produced from phialides
- SPORANGIOSPORES: spores formed by zygomycetes and are released when a mature sporangium ruptures
Fungi asexual spores:
What are the 4 colony features that fungi typically show?
- cottony
- velvety
- granular
- glabrous
In what 3 ways can fungal topography be described?
- rugose
- umbonate
- verrucose
What 3 structures do hyphae typically undertake?
- favic chandeliers
- racquet hyphae
- spiral hyphae
What 8 factors can predispose to fungal invasion of tissues?
- immunosuppression
- prolonged antibiotic therapy
- immunological defects
- immaturity, aging, malnutrition
- exposure to heavy challenge of fungal spores
- traumatized tissue
- persistent moisture on skin surface
- neoplasm
What are the 3 mechanisms involved in fungal disease?
- tissue invasion (mycosis)
- toxin production (mycotoxicosis)
- induction of hypersensitivity
In what 3 ways are fungal diseases categorized according to sites of infection?
- SUPERFICIAL: epidermis, other keratinized structures, mucous membranes (Dermatomycosis - Candida, Microsporum, Trichophyton)
- SUBCUTANEOUS: subcutaneous tissue (Phaeohyphomycosis, mycetoma)
- SYSTEMIC: respiratory and GI tracts and other organ systems (saprophytic, antimicrobial therapy)
What samples are typically taken for fungal infection diagnosis? What are 2 common stains used?
- hair
- skin
- biopsies
- Periodic acid-Schiff
- methanamine silver impregnation
How are fungi prepared for direct microscope observation? Spores?
wet preparation in 10% KOH
lactophenol cotton blue
Direct microscopy examination:
