Fungal Fundamentals Flashcards
two forms of pathologic fungi
**morphological terms but no taxonomic significance; some organisms are dimorphic (yeast when warmer, moulds when colder)
-moulds
-yeasts
Microbiological characteristics
-nucleated
-fungal hyphae (cell walls composed with chitin)
-cell membranes- contain ergosterol as main sterol
Environments
-aerobic
-grow at low temp (20-30C)
-high pressure
-low pH
-play a role in carbon cycle
-degrad polymers (biopolymers in wood, synthetic polymers)
Virulence factors
- tissue invasion
-mycosis - Toxin production
-mycotoxicosis - Hypersensitivity
-moulds grow in damp buildings; exacerbate asthma or hypersensitivity pneumonitis
Mycotoxicosis
- Aflatoxicosis- aflatoxins in feed affect poultry
- Fusariotoxicosis- zearalenone is non toxic for poultry but causes disease in pigs
- Ergotism- alkaloids produced by fungi growing on cereals
Taxonomy
-based on morphology and sexual reproductive cycles
-increasingly relying on DNA sequencing
Hyphae
filaments which make up mycelium
Mycelium
a mat of branching hypha
Asexual spores
disseminated to other locations and germinate when conditions are favourable
-spores will develop on different structures with different morphologies
Pathogenicity of fungi
Very few are pathogenic to mammals
-fungi are opportunistic not contagious
*Dermatophytes are common and contagious
-common cause of disease in ectotherms (plants, insects, fish, amphibians)
-not much effect on endotherms because body temperature is high
Fungi in mammals
- Commensal/host associated
-disease in states of immunosuppression
-candida, Malassezia - Environmentally acquired
-dimorphic fungi
-disease following exposure to large inoculum
-Blastomyces
Dinosaurs and fungal impact
-nuclear winter from asteroid killed plants
-large scale deforestation at K/T boundary; fungal breakdown of plants
-dinosaurs loss of plants, inability to warm up (ectotherms), immunosuppression and massive fungal spore plumes
-warm blooded animals (early mammals and birds) were protected by higher temp and ability to eat seeds
**Epidemiological Triad
White nose syndrome in North American Bats
-caused by Pseudogymnoascus destructans
-first studies at Usask
-huge mortality in bats
Chytridiomycosis
-threatens amphibians on every continent
-caused by Batrachonchytruym dendrobatidis; thought to originate in Xenopus laevis which were resistant and were able to pass it on
Snake fungal disease
-emerging in US but found in museum specimens in 1940s
-caused by Ophidiomyces ophiodiicola
-hard to find impact because snakes are reclusive animals