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Introduction to Mycology Flashcards

1
Q

Mycology

A

Defining Characteristics of Fungi

Structure (what do they look like, what are they made of?)
Sex (How do they reproduce and spread?)
Sustenance (How do they acquire nutrients?)

Fungal Diversity

Classification – True Fungi
- Fungus-like organisms
Economic / Medical / Industrial importance

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2
Q

What are Fungi?

A

Yeast
Mushrooms
Mould

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3
Q

Why study fungi?

A

Food Security
Health e.g Ring worm/athletes foot
Decomposition e.g nutrient recycling/dry rot
Biotechnology e.g food/drink industry or Therapeutics (e.g. Antibiotics)

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4
Q

Biodiversity

A

At least 1.5 million
different species of
fungus

Only 5% (75,000
species) have been
described to date

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5
Q
  1. All fungi are eukaryotic
A
  • Membrane bound nuclei containing
    several chromosomes
  • Membrane bound cytoplasmic
    organelles (mitochondria, vacuoles
    etc.)
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6
Q
  1. Fungi typically grow as filaments
A

Hyphae (singular hypha)
Fungi exhibit apical growth (Extend only at their extreme tips)

Septation

  • Hyphae grow apically,
  • Become divided at intervals
  • Transverse walls or septa → compartments or ‘cells’.
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7
Q

Mycelium

A

A network of branched hyphae

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8
Q

Mycelial growth

A

Mycelium – the fungal ‘body’ – consists of hyphae
Hyphal diameter 2 – 30 μm (5-10 μm usually)

1)Spore Germinates (stored C,N)
2)Hyphae grow radially forming a mycelium, a fungal colony (Tips grow outwards, maintain spacing,
seek and absorb C, N)
3|As mycelium ages,older hyphae are
consumed - autolysis (Mycelium fragments, spores form)

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9
Q

Differentiation

A

Fruiting body
Differentiates from mycelium
Forms and releases spores

Mycelium
Formed from hyphae
growing over and into
substrates, harvesting
nutrients

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10
Q

Fungi sometimes grow as yeasts

A

Single-celled yeast.
Saccharomyces cerevisiae
Reproduce by budding

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11
Q

Dimorphic fungi (2 shapes)

A

Some fungi switch between a budding yeast & hyphal phase in response to environmental conditions.

Include several pathogenic species of humans

Candida albicans

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12
Q
  1. Distinctive wall components
A

Chitin and β-glucans (polymers of glucose) = insoluble core of fungal cell wall

Confer RIGIDITY

Great targets for antifungal treatments

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13
Q
  1. Fungi are Heterotrophs
    (chemo-organotrophs)
A
  • The cell wall prevents fungi from
    engulfing food by phagocytosis
  • Fungi secrete degradative enzymes & absorb simple, soluble nutrients through the wall and cell membrane.
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14
Q
  1. Storage compounds
A
  • Lipids
  • Mannitol (sugar alcohol)
  • Glycogen
    *Trehalose (disaccharide of glucose)
    Conversion of energy to
    trehalose makes the energy
    unavailable to other microbes
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15
Q
  1. Haploid nuclei (1n)
A

Hyphae can house
several nuclei

Some stages of fungal life-cycles are diploid

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16
Q
  1. Sexual and asexual reproduction
A
  • Small asexual spores for dispersal
    *Large sexual spores for survival and diversity
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17
Q

Mycota (true fungi)

A
  1. Eukaryotic (membrane bound organelles)
  2. Hyphae with apical growth or yeasts
  3. Walls composed of chitin and glucans
  4. Heterotrophic.
  5. Unique storage compounds (eg trehalose)
  6. Haploid genome
  7. Asexual & sexual reproduction - Produce spores
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18
Q
  1. Phylum Zygomycota
A

Mainly saprotrophs
Found in soil / animal dung / soft fruits
e.g Rhizopus stolonifer

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19
Q

Zygomycota Hyphae

A

Hyphae lack cross walls

All nuclei contained
within a common cytoplasm

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20
Q

Zygomycota sexual reproduction

A

The production of a thick-
walled resting spore:
The zygospore

Formed by a sexual process involving
the fusion of two gametangia.

21
Q
  1. Phylum Ascomycota (Sac Fungi)
A

Very diverse forms
Aleuria
Helvella
Tuber

22
Q

Ascomycota Hyphae

A

Highly Septate

Cross walls with a central
pore for passage of nuclei
and other cellular organelles

23
Q

Ascocarp – fruiting body

A

Ascus formation usually within a complex structure
composed of tightly interwoven hyphae

Cleistothecium:
Closed and spherical

Perithecium:
Flask shaped,
e.g. Sordaria

Open & cup-shaped
(“apothecium”)

24
Q

Ascomycota Sexual reproduction

A

Asci produced from Ascogonium
Two haploid nuclei fuse to form a
diploid nucleus
Ascospores -Haploid sexual spores
Mitosis produces 8 ascospores
Meiosis forming 4 1n nuclei

25
Ascomycota mitospores
* Non motile asexual spores * Conidiospores Dispersal e.g. Aspergillus fumigatus – no sexual stage identified
26
Ascomycota plant pathogens
Claviceps purpurea Toxigenic ergots of cereals (St Anthony’s fire) Vascular wilt fungi Dutch Elm disease Swept across Europe and the USA
27
Ascomycota Human Pathogens
Dermatophytic fungi infect 50% total human population Tinea corporis: Ring worm Ascomycetous yeast, Candida albicans common commensal organism in the gut and other mucosal membranes of humans
28
3. Phylum Basidiomycota
37% of the true fungi identified
29
Basidomycota - Hymenomycetes
Degrade Cellulose & Lignin Woody Brackets Poisonous / Delicious (Agaricus bisporus “Portabello'') Toadstools (Amanita phalloides “Death cap”)
30
Basidiomycota Hyphae
Complex dolipore septum prevents nuclei moving between hyphal compartments. Each compartment contains two haploid nuclei (different mating compatibility groups)
31
Sexual reproduction (Basidiomycota)
All Basidiomycota produce a basidium in which meiosis occurs. Leading to the production of sexual spores Basidiospores are usually produced externally on short stalks termed sterigmata
32
Asexual reproduction (Basidiomycota)
* Asexual spores rarely produced * Conidia or oidia
33
Basidiomycota human pathogens
* E.g. Cryptococcus fungi Life threatening in people with impaired immune defences Cryptococcal meningoencephalitis >15% of HIV-related deaths worldwide
34
Basidiomycota plant pathogens
E.g. Puccinia graminis: Black stem rust of wheat
35
4. Mitosporic fungi
Deutromycota - Fungi Imperfecti Ascomycota / Basidiomycota) Spores produced by mitotic nuclear division Unknown Sexual stage
36
Plant pathogens / food spoilage
Fusarium oxysporum Aspergillus flavus Produce Aflatoxins (mycotoxins)
37
Mitosporic human / insect pathogens
Aspergillus fumigatus Long term lung infections (human) Metarhizium & Beauveria Capable of degrading exoskeleton
38
Fungus-like species CONVERGENT EVOLUTION
Similar lifestyle to fungi but many similarities to plants
39
1. Oomycota (500-800 species)
Most economically important plant pathogens * "Oomycota" means "egg fungi", referring to the oversize oogonia which house the female gametes (eggs)
40
Oomycota Hyphae
Fungal features - Apical Growth - Produce cell-wall degrading enzymes hyphae are broad fast growing lacking septa. Plant features: - Glucan cell walls - Diploid nuclei - Membranes composed of sterols - Plant-like organelles and storage compounds
41
Sexual Reproduction (Oomycota)
Male sex organ (antheridium) Female sex organ (oogonium) Fertilisation: transfer of single haploid nuclei through fertilisation tube
42
Asexual reproduction (Oomycota)
Multinucleate sporangium
43
1. Plasmodial slime moulds
Myxomycota: Wall-less Multinucleate network of protoplasm Found on moist rotting wood Engulf bacteria
44
Plasmodium formation
Haploid spores in fruiting body germinate to produce either amoeboid cells or flagellate swarmers Which fuse in pairs to form a plasmodium
45
Nutrient depletion – Fruiting body
n response to nutrition depletion; the whole plasmodium converts into fruiting structures (sporangia) that contain haploidspores that can start the whole process again
46
2. Plasmodiophorids
Obligate intracellular parasites of plants, algae or fungi. Grow only in host organisms e.g. Plasmodium brassicae Clubroot disease: large “galls” Root response to infection: * Hypertrophy: Rapid plant cell expansion * Hyperplasia: Rapid cell division Plant nutrients diverted to galls severely reducing shoot growth and yields Unmarketable crops
47
3 & 4. Cellular Slime Moulds
* Two groups: Dictyostelid & Acrasid * Both grow and divide as haploid unicellular amoeba
48
Behaviour
Phagocytosis: Engulf food e.g. bacteria Aggregation: At the onset of starvation, a few amoeba act as an aggregation centre. The amoebae then undergo streaming along defined tracks to aggregate as a mound.

Microbiology (10 decks)

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