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Microbiology BIO-5015B > Lecture 20: Fungal Physiology and Life Cycles > Flashcards

Lecture 20: Fungal Physiology and Life Cycles Flashcards

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1
Q

What are fungi?

A

animals and plants closely associated, branch off from fungi.

Eukaryotes

“any of a group of spore-producing organisms feeding on organic matter, including moulds, yeast, mushrooms, and toadstools.”

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2
Q

What are fungi?

A

animals and plants closely associated, branch off from fungi.

Eukaryotes

“any of a group of spore-producing organisms feeding on organic matter, including moulds, yeast, mushrooms, and toadstools.”

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3
Q

What are some unique characteristics of fungi?

A
  1. Unique lysine synthesis method
    • AAA pathway
    • AminoAdipic Acid pathway
    • Animals = DAP pathway
  2. Ridged cell wall composed of beta-1,3
    and beta-1,6 linked glucans, mannan
    and chitin
  3. Cell membranes contain “ergosterol”
    (animals have cholesterol, plants have
    sitosterol) - OFTEN A TARGET FOR
    TREATING FUNGAL INFECTIONS
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4
Q

What are the 5 major fungal phyla?

A
  1. Basidiomycota
    a. Most mushrooms, other
    macroscopic fungi in this group
  2. Ascomycota
    a. Industrially important
    b. e.g., penicillium (prod penicillin)
    c. e.g., aspergillus (prod of chemicals)
    d. Some macroscopic, most moulds
  3. Glomeromycota
    a. New phylum
    b. Mycorrhizal fungi
    c. Important symbiotic relationship
    with plants
  4. Zygomycota
    a. Pin-head fungi
  5. Chytridiomycota
    a. water fungi
    b. Mostly saprotrophs, some pathogen
    c. Batrachochytrium dendrobatidis =
    causes chytridiomycosis
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5
Q

What is the structure of fungal form?

A 
1. Most fungi are filamentous, made of 
   "tubular", thread-like "hyphae"
2. Mass of hyphae is termed "mycelium"
3. Sometimes large macroscopic bodies 
    are produced
4. Some fungi unicellular
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6
Q

What are hyphae?

A
  1. growth occurs at tips of hyphae
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7
Q

What is the structure of hyphae?

A
  1. Made of a thin transparent tubular cell
    filled or lined with protoplasm.
    a. Diameter: 1-30um
  2. Hyphae are colourless (hyaline), fungal
    colonies are coloured due to
    pigmentation in spores
  3. Tapered at the tip, called “extension
    zone”
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8
Q

Where are hyphae located and where is the reproductive structure located?

When are reproductive structures produced?

A

Hyphae everywhere. Make up the fibrous “body”/structure

Reproductive structure: The head of the mushroom - spores located underneath the lip

Reproductive structures produces when moist and not too hot (autumn)

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9
Q

Where are hyphae located and where is the reproductive structure located?

When are reproductive structures produced?

A

Hyphae everywhere. Make up the fibrous “body”/structure

Reproductive structure: The head of the mushroom - spores located underneath the lip

Reproductive structures produces when moist and not too hot (autumn)

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10
Q

What is the role of fungal cell walls?

A
  1. Determine the shape of the fungus
  2. Act as an interface between the fungus
    and its environment
  3. Protect against osmotic lysis, regulates
    passage of large molecules
  4. Antigenic properties that can mediate
    with the other organisms
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11
Q

What is the composition of fungal cell walls?

A
  1. 80-90% polysaccharides
  2. The chytridiomycota, ascomycota and
    basidiomycota have “chitin”.
  3. Zygomycota have mixture of “chitin” and
    “chitosan”
Chitin - polymer of N-acetylglucosamine
   a. also found in insect exoskeletons
Chitosan - polymer of D-glucosamine
   a. deacetylated form of N- 
      acetylglucosamine
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12
Q

How is fungal cell walls strucutred/designed?

A

Four zones

  1. Amorphous glucans
  2. glycoprotein + protein
  3. Protein
  4. Chitin + protein
  5. Plasma membrane
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13
Q

What is the septa?

A 
1. In most species; hyphae are 
    interrupted by cross-wall called 
    "septa"
2. Septa are usually perforated - 
    allowing passage of cytoplasm, and 
    even nuclei between parts of hyphae 
3. May act as structural report
4. May be first line of defence against 
    damage

“SIMPLE” = septum has large central pole (Ascomycota)
“DOLIPORE” = septum (Basidiomycota), narrow central pole, flanked by bracket-shaped membranes called “PARENTHOSOMES” (clamp connections)
a. does not allow passage of nuclei,
ensures dikaryotic condition

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14
Q

What are Woronin bodies?

A
  1. Form just behind each septum
  2. Proteinaceous lattices surrounded by a
    membrane
  3. Plug the sepal pores if the hyphae are
    damage, becoming old or undergoing
    differentiation
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15
Q

What is differentiation in fungi?

A
  1. Dimorphism
  2. Development of structures involved in
    sexual reproduction
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16
Q

What is meant by dimorphism in fungi?

A
  1. Can change between yeast and mycelial
    form
  2. Common for animal and human fungus
    pathogens:
    a. filamentous outside host
    b. single cell inside the host
  3. change from filamentous to yeast form
    can be bought about by changing the
    environmental conditions (e.g., oxygen,
    sugar, calcium concentrations)

E.G., Candida albicans grows as a yeast in moist mucosal membranes of humans, but converts to hyphal to invade tissues

17
Q

What is meant be apical growth

A 
1. Fungal hyphae extend continuously at 
   extreme tips
2. Growth supported by continuous 
    movement of mineral into the tip from 
    the older regions of hyphae
3. Hyphae are a continuous movement of 
    protoplasm, which thrusts the growing 
    tip forward
18
Q

What is the mechanism of apical growth?

A
  1. Growing tip of hyphae contains very few organelles, instead contains a body called “spitzenkorper” (apical body)
  2. This consists of a cluster of small, membrane bound vesicles embedded in a meshwork of actin microfilaments
  3. Its always present in growing tips, disappears when growth stops and reappears if growth restarts
19
Q

How do fungi acquire nutrients?

A 
1. Small organic food molecules 
   transported across plasma membrane
2. Polymeric food molecules must be 
    depolymerised
3. Depolymerizing enzymes are secreted 
    by vesicles fusing with the membrane
20
Q

How and what two sexual processes do fungi perform?

A
  1. Sexual reproduction
  2. Asexual reproduction

Spores are essential for this.

21
Q

How does asexual reproduction occur in fungi?

A
  1. Germination
  2. Mycelium (n)
  3. Spore producing structures (n)
  4. Spores (n)
  5. Repeat
22
Q

How does sexual reproduction occur in fungi?

A
  1. Dikaryotic stage (n+n)
  2. Karyogamy (function of nuclei)
  3. Diploid stage (2n)
  4. Meiosis
  5. Spore producing structures (n)
  6. Spores (n)
  7. Germination
  8. Mycelium (n)
  9. Plasmogamy (fusion of cytoplasm)
  10. repeat
23
Q

What are fungal mating types?

A
  1. Fungal mating types are determined by:
    “mating-type locus”
  2. Different mating types of fungi look the
    same.
24
Q

Why are spores “dispersed”?

A 
1. To extend beyond the existing 
   environment
   a. escape nutrient depletion
   b. Exploit new potential environmental 
       niches
25
Q

What are spores?

A
  1. Can be produced either sexually or asexually

2. Diverse; size, shape, structure, and colour

26
Q

How are spores designed?

A
  1. Propelled far enough beyond the
    surrounding fruiting body
  2. Remain suspended in air currents to be
    distributed appropriately
  3. For small spores, take-off is limited by
    drag, do high launch speeds is required
27
Q

What disperses spores?

A
  1. Wind of air currents - most species
  2. Water - aquatic fungi
  3. Animals - vertebrates and invertebrates
  4. Host plants - particularly seeds

Before dispersal, all spores have to be released this is either active or passive

28
Q

What is active liberation?

A
  1. Spores released from the hymenium

(spore producing surface)

29
Q

What is passive spore liberation?

A
  1. External factors:
    a. wind
    b. rain
    c. animals
30
Q

What is the purpose of rain splash for fungi?

A
  1. Puff balls such as Lycoperdon (stump
    puffball)
  2. Spores produced in a sack like peridium
  3. When mature, peridium ruptures at
    the apex and water droplets depress
    the peridium, shooting a puff of
    spores into the air
31
Q

What is meant by insect dispersal?

A
  1. The stinkhorn, smells of rotting flesh, but
    also contains lots of sugars which attracts
    flies
  2. Spores pass through gut of insect,
    unharmed, dispersed via defecation
  3. Some fungi are naturally florescent
  4. this luminescence attracts insects

Microbiology BIO-5015B (30 decks)

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