Eukaryotic Microbes 2: Fungi Flashcards Preview

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Flashcards in Eukaryotic Microbes 2: Fungi Deck (23):

Where are fungi found?

- Everywhere!
- aquatic
- terrestrial
- parasites of plants
- parasites of animals and humans


Explain the fungal nucleus.
- size
- ploidy
- unique features of the fungal nuclei?

- double membrane bound organelle ranging in size from 1-2um to 20-25um in diameter
- most are haploid with 6-20 chromosomes
L> some are naturally diploid
L> others alternate between the two
-membrane remains intact during mitosis
L> no clear metaphase plate.


Fungal cytoplasmic organelles?

- plasma membrane
L>phospholipid bilayer -> anchorage for enzymes/proteins such as chitin synthases or glucan synthases
L> contains ergosterol
- chitosomes
L> microvesicles for chitin synthesis


Explain the purpose of the fungal cell wall.

- structural barrier
- environmental interface
L> protects against osmotic lysis
L> contains pigments for protection
L> binding site for molecules
L> mediates interactions with other organisms.


Describe the composition of the fungal cell wall.

- Mannan
- protein
- B-1,3-glucan
- chitin

**58%= glucan
**36%= Mannan
** 4% = protein
** 2 %= chitin
** be able to draw the cell wall and label these areas.


With respect to the fungal cell wall what does Mannan give it?

- a detectable signature via:
1. O-Mannan -> composed of alpha 1,2 mannose and beta 1,2- mannose.
2. N-Mannan -> composed of alpha 1,2 mannose, beta 1,2- mannose, N acetyl glucosamine, beta 1,4 mannose, alpha 1,6 mannose, alpha 1,3 mannose and Phosphate.... aka IT IS MORE COMPLEX


The growth of fungi:
- What can they look like ( three groups)

1. Filamentous
L> moulds and mushrooms
2. Yeasts (circular shape)
3. Dimorphic fungi (mixture)


Describe filamentous fungi!
- what is the main structure?

-Hyphae: rigid tubes containing cytoplasm. Interconnected compartments not individual cells
- long filaments of cells joined end to end = hyphae


Filamentous fungi:
- Describe the two types of hyphae.

1. Septate Hyphae
L> joint cells have distinct separations called septa, containing pores (to share cytoplasm)
2. Coenocytic Hyphae
L> consists of fused cells, multinucleated


Filamentous fungi:
- function of septa?

- offers structural support
- enables differentiation by dividing hyphae into different cells


Filamentous Fungal growth:
typically goes _____ to ____.

- spore to hyphae


Filamentous Fungal growth:
-hyphae typically grow in what fashion?

- by apical growth : extension at the tip


Filamentous Fungal growth:
- what is a mass of hyphae called?

- mycelium --> plural = mycelia


Filamentous Fungal growth:
- Explain vegetative and aerial hyphae.

- vegetative hyphae:
L> grow along the surface , obtain nutrients
- Aerial hyphae:
L> stick up from the mycelium, spores for reproduction


Explain the tropisms of hyphal tips.

- they exhibit it to many substances
L> Ex: nutrients, amino acids, volatile metabolites, sex pheromones and light
L> examples species = Phycomyces blakesleeanus (phototropism I believe- double check)


- explain their characteristics.

- non-filamentous, unicellular, ovaloid
- facultative anaerobes
L> aka ferment carbohydrates into alcohol and carbon in the absence of oxygen.


- explain budding yeast.

- divide by producing outgrowth called a bud
- bud enlarges and separates from mother cell (vegetative cell)
- if budding fails = pseudohyphae


- explain true hyphae and pseudohyphae

- True Hyphae: cells tightly attached by shared walls, cytoplasm joined via pores.
-Pseudohyphae: daughter cells remain attached to the mother cell but do NOT share cytoplasm (formed via the failed attempt at budding)


- Explain fission yeast.

- division by elongation of mother cell and mitosis
- daughter cells separate by the formation of septa in the centre
ex: Schizosaccharomyces pombe


- explain dimorphic yeast.

-grows as multicellular hyphal or as unicellular yeast depending on the conditions


Several Pathogens of humans exhibit dimorphism. Give three examples.

1. Candida albicans
2. Histoplasma capsulatum
3. Mucor circinelloides


Dimorphism occurs in response to a variety of environmental factors. Apply this statement to the following three species:
1. Histoplasma capsulatum
2. Candida albicans
3. Mucor circinelloides

1. 27C = filamentous; 37C= yeast
2. human body = filamentous
3. oxygen = filamentous; hypoxia = yeast


Approx how many species?

1.5 million