Topic 8: fungi

Question 1

Types of fungi

Answer 1

• Unicellular = yeasts
• Multicellular = mushrooms/molds

Question 2

Describe multicellular fungi

Answer 2

• Non-motile
• Environments = moist/humid/aquatic
• Growth temp = 2-20 °C
• Heterotrophs = absorb nutrients from external environment
• Saprophytes = nutrients from dead organic matter = decomposers

Question 3

Describe the fungal morphology

Answer 3

• Cell wall = chitin
• Body = multicellular filiments/ unicellular fungi
• Dimorphism = some species can grow both body types depending on environmental conditions

Question 4

Describe yeasts

Answer 4

• Form multicellular colonies
• Reproduce = sexual/asexual budding
• E.g. Saccharomyces cerevisiae

Question 5

Describe the structure of multicellular fungi

Answer 5

• Have filamentous structure = mycelia = network of branched filaments
• Filaments = hyphae = aid nutrient absorption

Question 6

Types of hyphae

Answer 6

1) Septate = has septa
- Septa = rings of hyphae cell walls
- Most fungi hyphae divided into cells by septa
- Pores = cell>cell movement of organelles
2) Coenocytic = no septa
- Continuous cytoplasmic mass = 100/1000s of nuclei

Question 7

Describe fungal reproduction

Answer 7

• Via spores
  ASEXUAL:
• Simple cell division = binary fission = mitosis
• Budding = new organism develops from outgrowth = separates from paretal cell
• Spore n > spore n
  SEXUAL:
• Produce diploid zygote via fusion of 2 haploids = meiosis
• Zygote 2n > spores n

Question 8

Define germination

Answer 8

• Under favorable conditions = spores grow to vegetative cells

Question 9

Explain sexual reproduction of fungi

Answer 9

• Fungal nuclei = haploid
• Exception = temporary diploid stages during life cycle
• Fusion of hyphae from different mating types
• Fungi use sexual signaling molecules = pheromones = communicate mating type
• Plasmogamy = union of cytoplasm from 2 parent mycelia
• Heterokaryon = mycelium in which haploid nuclei from each parent coexists = not fused
• Karyogamy = fusion of haploid nuclei = diploid cell

Question 10

Explain asexual reproduction of fungi

Answer 10

• Yeasts via simple cell division + budding
• Molds via haploid spores + mitosis = e.g. conidia
• Form mycelia

Question 11

What are yeasts and molds called?

Answer 11

Deuteromycetes

Question 12

Explain the origin of fungi

Answer 12

• Form opisthokont clade = Unicont supergroup
• Fungi + animals + protists = common ancestors

Question 13

5 fungal categories

Answer 13

1) Chytrids
2) Zygomycetes
3) Glomeromycetes
4) Ascomycetes
5) Basidiomycetes

Question 14

Describe zygomycetes

Answer 14

• Has spore producing structures:
  > Sporangia = produce spores via asexual
  > Zygoporangia = sexually produced spores + resistant to freezing/drying = can survive under unfavorable conditions
• E.g. black bread mold

Question 15

Describe glomeromycetes

Answer 15

• Form arbuscular mycorrhizae
• Mycorrhizae = mutually beneficial relationships between fungi + plant roots
• Arbuscular mycorrhizal fungi = specialized hyphae = haustoria = penetrate cell wall of root cells
• Mutualistic relationship = fungi deliver phosphate ions +minerals to plants

Question 16

Describe ascomycetes

Answer 16

• Produce spores via sexual/asexual
• E.g. bread mold Neurospora crassa + morels + truffles
• Spore-producing structures:
  1) Asci = produce sexual spores
• Location = ascocarps = fruiting body
  2) Conidiophores = specialized hyphae produce asexual spores

Question 17

Define fruiting body

Answer 17

• Multicellular structure = has spore producing structures

Question 18

Describe basidiomycetes

Answer 18

• Club fungi = clublike structure = basidium
• Basidia = sexual spore producing structure
• Basidiocarp = fruiting body = many basidia
• E.g. mushrooms

Question 19

What are the functions of fungi?

Answer 19

1) Decomposers
2) Mutualists
3) Parasites

Question 20

Explain fungi as decomposers

Answer 20

• Produce enzymes = breakdown complex molecules + dead organic material > smaller compounds
• Produce CO2 + nitrogen fixation
• Important to nutrient recycling
• Maintain ecological balance

Question 21

Explain fungi as mutualists

Answer 21

• Relationships with plants/algae/cyanobacteria/ animals
• Fungi + plant = mycorrhizae
• Fungi + animal = digestive system
• Fungi + microorganisms = in lichens
• Beneficial ecological effect

Question 22

Describe the mutualistic relationship between fungi + lichen

Answer 22

• Symbiotic association between photosynthetic microorganisms + fungus

Question 23

Describe pathogenic fungi

Answer 23

• 30% fungal species = mostly plant pathogens
• Some plant pathogens fungi = toxic to human
  TYPES:
  1) Pathogenic zygomycetes
  2) Pathogenic ascomycetes
  3) Pathogenic basidiomycetes

Question 24

Describe pathogenic zygomycetes

Answer 24

• Cause skin/ear infections + bronchitis-pneumonia
• E.g. genera Μucor + Rhizopus + Absidia

Question 25

Describe pathogeneic ascomycetes

Answer 25

1) Aspergillus flavus: - Produce mycotoxins = aflatoxins - Aflatoxin B1 = liver cancer due to p53 mutations - Infect peanuts + wheat 2) Claviceps purpurea: - Produce ergotamine + lysergic acid = LSD synthesis - Psychotropic effect +convulsions + gangrene - Infect cereals

Question 26

Describe pathogenic basidiomycetes

Answer 26

- E.g. Amanita phalloides = poisonous mushrooms - Contain lethal toxins: > α-amanitin = inhibits eukaryotic RNA pol II > Phalloidin: inhibits F-actin polymerisation - E.g. Αmanita muscaria + Psilocybe cubensis = magic mushrooms = psychoactive mushrooms

Question 27

Define mycoses

Answer 27

Human fungal infections

Question 28

4 types of human mycoses

Answer 28

1) Superficial-cutaneous 2) Subcutaneous 3) Systemic 4) Opportunistic

Question 29

Describe superficial cuaneous mycoses

Answer 29

- Infection of hair/nail/skin - E.g. Microsporum furfur = ascomycete = ringworms - E.g. Trichophyton + Epidermophyton = athlete's foot

Question 30

Describe subcutaneous mycoses

Answer 30

- Due to trauma

Question 31

Describe systemic mycoses

Answer 31

- Spread via blood stream to sites/organs - Commonly = respiratory infections > other organs - E.g. Coccidioidomycosis = caused by Coccidioidesimmitis = produces TB-like symptoms - E.g. Histoplasmosis: caused by Histoplasma capsulatum - E.g. Cryptococcosis: caused by Cryptococcus neoformans - E.g. Blastomycosis: caused by Βlastomyces dermatitidis - E.g. Geotrichosis: caused by Geotrichum candidum

Question 32

Describe oportunistic mycoses

Answer 32

- Via fungi part of normal flora = normally non-pathogenic - Become pathogenic + cause infection = in immunosuppressed individuals - E.g. yeast Candida albicans = causes candidiasis = skin + vaginal + mouth infection/thrush

Question 33

What are the industrial/therapeutic applications of fungi?

Answer 33

- Production of antibiotics - Production of alcoholic beverages + bread + cheese - Genetic engineering

Question 34

Explain application of fungi in producing antibiotics

Answer 34

- From ascomycetes of genus Penicillium - Penicillium chrysogenum = produces penicillin = antibacterial antibiotic -Penicillium griseofulvum = produces griseofulvin = antifungal antibiotic

Question 35

Explain application of fungi in producing food + drink

Answer 35

- From yeast Saccharomyces cerevisiae - Produce enzymes used for alcohol fermentation - CO2 production in baking yeast

Question 36

Explain application of fungi in genetic engineering

Answer 36

- Insulin-like growth factors = produced in fungus Saccharomyces cerevisiae - Study of genes involved in human diseases