Topic 7B: Fungi ✅ Flashcards Preview

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Flashcards in Topic 7B: Fungi ✅ Deck (56)
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1
Q

What are fungi?

A

Eukaryotic microorganisms

2
Q

Fungal types

A

Unicellular: Yeasts (eg Saccharomyces cerevisiae)

Multicellular (eg mushrooms, molds)

3
Q

Multicellular fungi characteristics

A

Non-motile

Usually live in moist, humid or aquatic environments

Growth temperature: 2-20 degrees

Heterotrophs: absorb nutrients from their external environment

*some are saprophtes (decomposers): obtain their nutrients from dead organic matter

4
Q

Fungal morphology

A

Cell wall made of chitin

Body structures:
-Multicellular filaments
-Unicellular fungi

Dimorphism: some fungal species (eg Blastomyces) can grow both as filaments or yeasts depending on environmental conditions

5
Q

Yeasts

A

Unicellular fungi

-usually form multicellular colonies

-reproduce using asexual reproduction (e.g. budding)

Eg Saccharomyces cerevisiae

6
Q

Multicellular fungi

A

Filamentous structure: consist of mycelia

-filaments = hyphae (Septate, Coenocytic fungi [lack septa])

Mycelia: forma of branched hyphae => aid nutrient absorption and then become sporangia to produce spores

7
Q

Fungal reproduction overview

A

By either sexual or asexual by producing spores

Asexual:
-simple cell decision (aka binary fission)
-Budding: new organism develops from outgrowth (bud) that separates from parent cell

Sexual reproduction:
-production of diploid zygote (2n) by fusion of haploid (n) fungi (hyphae)

8
Q

How can haploid (n) sported be produced?

A

Sexually or asexually

Sexual: zygote (2n) —meiosis—> spores (n)
-called sexual spores

Asexual: spore (n) —mitosis—> spores (n)

9
Q

Germination

A

Under favourable conditions, spores grow back to the vegetative cell (fungal cell)

Spore —germination—> vegetative cell

10
Q

Fungal life cycle

A

SEXUAL REPRODUCTION
Plasmogamy (cytoplasmic fusion) (n)

-> Heterokaryotic stage (non-fused nuclei from 2 different parents)

-> Karyogamy (nuclear fusion), zygote (2n)

-> Meiosis, spores (n)

-> Germination

Through mycelium

Repeat

ASEXUAL
Through mycelium (n)

-> Spore producing structures

-> Spores

-> Germination
Repeat

11
Q

Asexual reproduction

A

Yeasts: reproduce mostly asexually by simple cell division and budding

Molds- produce haploid spores by mitosis (e.g. conidia)
-> form mycelia

12
Q

What are molds and yeasts called?

A

Deuteromycetes

-imperfect fungi

13
Q

What is the origination of Fungi?

A

Fungi, animals and their protist relative form the Opisthokonts clade (part of the Uniconts Supergroups)

14
Q
  1. Chytrids
A

Phylum Chytridiomycota

Characterized by zoospores: flagellated spores

Have hyphae

15
Q
  1. Zygomycetes
A

Phylum Zygomycota

Named after characteristic zygosporangia (e.g. black bread mold)

Spore-producing structures=

-Sporangia: produce spores by asexual

-Zygosporangia:
contain sexually produced spores (by karyogamy and meiosis)
Resist drying and freezing => can survive unfavorable conditions

16
Q
  1. Glomeromycetes
A

Phylum Glomeromycota

Mychoerrhizae: Mutualistic relationship between fungi and plant roots

Arbuscular mycorrhizal fungi: have specialized hyphae (called haustoria) that pentraate the cell walls of root cells

Mutualistic relationship: mycorrhizae fungi deliver phosphate ions and minerals to plants

17
Q

What is Arbuscular mycorrhizae formed by?

A

Glomeromycetes

18
Q

Ascomycetes

A

Phylum Ascomycetes
Sac fungi

Can produce spores by both sexual and asexual

Spore producing structures:

  1. Asci: -produced sexual spores (ascospores)
    -located in ascocarps (fruiting body)
  2. Conidiophores: specialized hyphae that produce asexual spores (conidia)

Eg bread mold Neurospora crasse, Morchella esculenta (tasty morel) and Tuubor melanosporum (truffle)

19
Q

Fruiting body

A

Multicellular

Reproductive structure

Contains spore-producing structures

20
Q
  1. Basidiomycetes
A

Phylum Basidiomycota

Club bacteria: characterized by a clublike structure called a basidium (transient diploid stage)

Basidia: spore-producing structures (only produce sexual spores [basidiospores])

Basidiocarp: fruiting body, has numerous basidia)
E.g. mushrooms

21
Q

Fungi function roles

A
  1. As decomposers:
    -Nutrient recycling between living and non-living
  2. As mutualists:
    -fungi -> animals: in the digestive system
  3. Pathogenic fungi
22
Q

Pathogenic Fungi

A
  1. Pathogenic Zygomycetes
    E.g. genera Mucor, Rhizopus, Absidia
    - causes skin and ear infections, bronchitis - pneumonia
  2. Pathogenic Ascomycetes
    I: Aspergillus flavus
    -produces mycotoxins such as aflatoxins
    -infects peanuts and wheat
    -Aflatoxin B1: liver cancer (due to p53 mutations)

II: Claviceps purpurea
-infects cereals (eg rye)
-produces ergotamine and lysergique acid (precursors fro LSD synthesis)
-> psychotropic effects (hallucinations, temporary insanity), convulsions, gangrene

  1. Pathogenic Basidiomycetes
    Amanita phalloides: poisonous mushrooms
    -contain lethal toxins (eg phalloidin, amanitin)

Amanita muscaria and Psilocybe cubensis aka magic mushrooms
-psychoactive mushrooms => causes hallucinations (psychotropic effects)

23
Q

Mycoses

A

Human fungal infections

Major types of human mycoses:

  1. Superficial: Cutaneous mycoses
  2. Subcutaneous mycoses
  3. Systematic mycoses
  4. Opportunistic mycoses
24
Q
  1. Superficial and cutaneous mycoses
A

More common

Fungal infections of hair, nails and skin

-Microsporum furfur: ascomycete that causes ringworm

-Ascomycete genera Trichophyton and Epidermophyton: causes athlete’s foot (ringworm of foot)

25
Q
  1. Subcutaneous mycoses
A

Subcutaneous fungal infection due to trauma

-Chromomycosis: caused by the fungi Hormodendrum pedrosoi, Hormodendrum compactum, Phialophora verrucosa

-Sporotrichosis: caused by fungus Sporotrichum schenckii

-Mycetoma: caused by fungi of the Aspergillus genus

26
Q
  1. Systemic mycoses
A

Fungal infection spread through blood stream to various sites/ organs of the body

Commonly cause respiratory infections initially, then spread to other organs

-Coccidioidmycosis: caused by Coccidioides immitis -> produces TB-like symptoms

-Histoplasmosis: caused by Histoplasma capsulatum

-Cryptococcosis: caused by Cryptococcus neoformans

-Blastomycosis: caused by Blastomyces dermatitidis

-Geotrichosis: caused by Geotrichum candidum

27
Q
  1. Opportunistic mycoses
A

More common

Caused by fungi that are part of our normal flora (saliva, skin, digestive system)

Normally non-pathogenic

Become pathogenic and cause infections only in immunosuppressed individus

-yeast Candida albicans: causes candidiasis
-> mouth infection (thrush), skin & vaginal infections

28
Q

Industrial and Therapeutic Applications of Fungi

A

Penicillium chrysogenum: produces penicillin (anti-bacterial anti-biotic)

-Penicillium griseofulvum: produces griseofulvin (anti-fungal antibiotic)

Production of alcoholic beverages, bread and cheeses

Genetic engineering

Antibiotic production by fungi: Ascomycetes of genus Penicillium

29
Q

Production of alcoholic beverages, bread and chees

A

Yeast Saccharomyces cerevisae

-production of enzymes used for alcohol fermentation
=> production of beer, wine etc

Also used for baking yeast (CO2 production)

30
Q

Genetic engineering and fungi

A

Insulin-like growth factor (IGF) can be produced by the fungus Saccharomyces cerevisae

Study of genes involved in human diseases

31
Q

Antibiotic production by fungi

A

Ascomycetes of genus Penicillium

The fungus Penicillium chrysogenum produces penicillin which kills Staphylococcus

=> produces zone of inhibition of Staphylococcus growth around its colonies on nutrient agar

32
Q

Septate

A

Hyphae type

With septa

Most fungi have hyphae divided into cells by septa

Septa= rings of hyphae cell walls
-pores allow cell-to-cell movement of organelles

33
Q

Coenocytic fungi

A

Aseptate

Hyphae type

Lack septa

Have continuous cytoplasmic mass with hundreds/thousands of nuclei

34
Q

What are fungal nuclei normally?

A

Haploid

Exception: transients diploid stages formed during the sexual life cycles

35
Q

Sexual reproduction of fungi

A

Fusion of hyphae from different mating types

Use sexual signaling molecules (pheromones) to communicate their mating types

36
Q

Plasmogamy

A

Union of cytoplasm from 2 parent mycelia

37
Q

Heterokaryon

A

Mycelium in which the haploid nuclei from each parent coexist (don’t fuse right away)

38
Q

Karyogamy

A

Fusion of haploid nuclei

=> production of diploid cells

39
Q

What is Penicillium?

A

Common mold

Food decomposer

40
Q

How many species of each type of fungal category are there?

A

Chytrids: 1,000

Zygomycetes: 1,000

Glomeromycetes: 160

Ascomycetes: 65,000

Basidiomycetes: 30,000

41
Q

Mutualistic relationships examples

A

Fungi - plants: Mycorrhizae

Fungi - animals: in digestive system

Fungi - microorganisms: in lichens

42
Q

Lichens

A

Symbiotic association between a photosynthetic microorganism (cyanobacterium/ green alga) and a fungus (eg an ascomycete)

Leaflike = foliose

Crustose = encrusting

Fruticose = shrublike

43
Q

Pathogenic Ascomycetes

A
  1. Aspergillus flavus
  2. Claviceps purpurea
  3. Pathogenic Basidiomycetes
44
Q
  1. Aspergillus flavus
A

-produces mycotoxins such as alfaltoxins

-infects peanuts and wheat

-Aflatoxin B1: liver cancer (due to p53 mutations)

45
Q
  1. Claviceps purpurea
A

-infects cereals (eg rye)

-produces ergotamine and lysergique acid (precursors for LSD synthesis)

=>psychotropic effects (hallucinations, temporary insanity), convulsions, gangrene

46
Q
  1. Pathogenic Basidiomycetes
A

-Amanita phalloides: poisonous mushrooms

-contain lethal toxins (eg phalloidin, amanitin)
=> alpha-amanitin: inhibits eukaryotic RNA pol II
=> Phalloidin: inhibits F-actin polymerisation

-Amanita muscaria and Psilocybe cubensis: magic mushrooms
=>psychoactive mushrooms -> cause hallucinations (psychotropic effects)

47
Q

Mycoses

A

Human fungal infections

48
Q

Major types of human mycoses

A
  1. Superficial-cutaneous mycoses
  2. Subcutaneous mycoses
  3. Systemic mycoses
  4. Opportunistic mycoses
49
Q

Superficial and cutaneous mycoses

A

Fungal infections of hair, nails and skin

Microsporum furfur: ascomycete, causes ringworm

Ascomycete genera Tricophyton and Epidermophyton: causes athlete’s foot (ringworm of foot)

50
Q

Opportunistic mycoses

A

Caused by fungi that are part of our normal flora (saliva, skin, digestive system) - normally non-pathogenic

Become pathogenic and cause infections only in immunosuppressed individuals

Eg Candida albicans: yeast, causes candidiasis
=> mouth infection (thrush), skin infection, vaginal infection etc

51
Q

Industrial and Therapeutic applications of Fungi

A

Production of antibiotics: eg Ascomycetes of genus Penicillium

Production of alcoholic beverages, bread and cheeses: eg the yeast Saccharomyces cerevisiae

Genetic engineering: eg insulin-like growth factor (IGF) can be produced in the fungus Saccharomyces cerevisiae

52
Q

Ascomycetes of genus Penicillium

A

-Penicillium chrysogenum: produces penicillin (anti-bacterial antibiotic)

-Penicillium griseopfulvum: produces griseofulvin (anti-fungal antibiotic)

53
Q

Production of alcoholic beverages, bread and cheeses

A

Eg the yeast Saccharomyces cerevisiae

-production of enzymes used for alcohol fermentation
=>production of beer, wine etc

-also used in baking yeast (CO2 production)

54
Q

Genetic engineering eg

A

Eg insulin-like growth factor (IGF) can be produced in the fungus Saccharomyces cerevisiae

Study of genes involved in human diseases

55
Q

Penicillium chrysogenum

A

Produces penicillin => kills Staphylococcus

=>produces zone of inhibition of Staphylococcus growth around its colonies on nutrient agar

56
Q

Which fungal phylum do mushrooms belong to?

A

Basidiomycetes