MICRO LEC: INTRO TO MYCOLOGY PT1 Flashcards
Study of fungi
Also important in food chain because they can decompose ded plant matter
FQ: OUT OF 100,000 species of fungi how many are pathogenic to humans and animals?
Mycology
fq: 200
They are Chemoheterotrophs; They are multicellular except ________?
fq: What are chemoheterotrophs?
How do they reproduce?
Fungi
yeast
FQ: requiring organic compounds for energy and carbon
They reproduce through sexual and asexual spores
non-photosynthetic heterotrophs which produce exoenzymes and obtain nutrients by absorption
Eukaryotic
(e.g. dermatophytes causing ringworms)
Parasitic
(decomposition of organic matter, causes sporadic opportunistic infections in animals)
Saprophytic
(obligatory association with other microorganisms; non-pathogenic)
Mutualistic
cause localized lesions
Overgrowth of yeasts (often commensals)
Can tolerate high osmotic pressures and acidic environments as low as pH 5.0 (optimum pH is about 6)
Fungi
Optimum temp. for growth of 20-30C; pathogenic ___ causing systemic mycoses can tolerate 37C
Fungi
cell type of fungi
Eukaryotic
cell type of bacteria
Prokaryotic
cell membrane of fungi
Sterols present
cell membrane: bacteria
Sterols absent; except in mycoplasma
cell wall: fungi
glucans; mannans; chitin (no peptidoglycan)
cell wall: bacteria
peptidoglycan
Spores: fungi
sexual and asexual reproductive spores
spores: bacteria
endospores (not for resproduction); some asexul resproductive spores
metabolism: fungi
limited to heterotrophic; aerobic, facultative anaerobic
metabolism: bacteria
heterotrophic; autotrophic; aerobic; facultatively anaerobic; anaerobic
Two main morphological fungal forms
Yeast vs. Molds
multicellular; vegetative and reproductive phases are two distinct phases; can grow as branching filaments called hyphae
Molds
Unicellular; the same cell function in vegetative growth (asexual) as well as in sexual reproduction; oval or spherical appearance
Yeast
a mass of threadlike filaments which combine to make up the fungal mycelium
Hyphae (singular: hypha)
In most molds, the hyphae contain cross-walls called _______ (singular: septum), which divide them into uninucleate cell-like units - _________
septa (singular: septum)
septate hyphae
in few class of fungi, the hyphae contain no septa and appear as long, continuous cells with many nuclei
Coenocytic hyphae
Impart rigidity and osmotic stability
FQ: Mainly composed of ?
Hyphal cell wall
fq:carbohydrate components including chitin micromolecules with cellulose cross- linkages
In yeasts, Hyphal cell wall contain
protein complexed with polysaccharides
Hyphal cell wall has Bilayer cell membrane, the predominant sterol is ________ in contrast to cholesterol
ergosterol
portion of hypha that obtains nutrients
Vegetative hypha
portion concerned with reproduction; projects above the surface of the medium on which the fungus is growing; often bear reproductive spores
Reproductive/aerial hypha
Nonfilamentous, unicellular fungi
Spherical or oval
Frequently found as a white powdery
coating on fruits and leaves
Yeasts
Explain budding
Parent cells forms a protuberance (bud) on its outer surface
Bud elongates and parent cell’s nucleus divides
One nucleus migrates into the bud
Cell wall material laid down between the bud and parent cell
But eventually breaks away
Some yeasts produce buds that fail to detach themselves. These buds form a short chain of cells called ?
pseudohypha
-If oxygen is present, yeasts perform aerobic respiration to metabolize carbohydrates into carbon dioxide and water
-If oxygen is absent, they ferment carbohydrates and produce ethanol and carbon dioxide.
-This fermentation is used in the brewing, wine-making and baking
facultative anaerobic growth in yeast
-Some pathogenic species of fungi can exhibit dimorphism (two forms)
-Moldlike form- produce vegetative and aerial hyphae
-Yeastlike form- reproduce by budding
Dimorphic Fungi
Dimorphism is temperature dependent; give the temperature, yeast and mold grow.
At 37C, the fungus is yeastlike
At 25C, it is moldlike
-Elongation at tips
-When a fragment breaks off, it can elongate to form a new hypha
Growth of a Hypha
-Large colonies with growth and extension of hyphae at their peripheries
-In some species, mature elements at the center of colonies produce aerial hyphae that facilitates dispersal of mature spores (e.g. conidia and sporangiospores)
Colony formation of Molds
are formed only by fungi in the phylum Zygomycota
Sporangiospores