Lecture 3: Fungi

Question 1

To what taxonomic group do fungi belong to?

Answer 1

most fungi belong to unikots -opisthokonts (together with animals)

Question 2

Where can fungi be found on the eukaryotic tree of life?

Answer 2

They are widely dispersed on the tree of life, however main linage of fungi (Eumycota) belongs to ‚Opisthokonts‘, probably sister to the kingdom of Animalia

Question 3

What is the main fungal linaege

Answer 3

• Microsporidia
• Chytrids (Chytridiomycota + some small lineages)
• Glomeromycota
• Zygomycota (also named Mucoromycotina)
• Dikarya: - Ascomycota (sac fungi)
• Basidiomycota (club fungi)

Question 4

Describe cell wall of fungi

Answer 4

• contains chitin
  
  • polymer of N-acetylglucosamine; increased strength/resistance to degradation as compared to cellulose
  • except in many yeasts (β-1,3-glucan/mannan a.o.), stramenopilan ‚fungi‘ (cellulose/ β-1,3- a β-1,6-glucan), myxomycetes

Question 5

Describe what nutrients fungi intake and how they store it

Answer 5

• heterotrophy: saprotrophy (organic material from dead organisms), parasitism, mutualistic symbiosis, fermentation
• primary storage polysaccharide: glycogen

Question 6

How do fungal cells perform mitosis

Answer 6

• nuclear mitosis: the nuclear envelope does not disintegrate and reform, but takes place within the nucleus
  
  • envelope constricted near mid point between daughter nuclei
• lack of centrioles, formation of spindle pole bodies

Question 7

How do fungi reproduce?

Answer 7

• sexual and asexual spores
• spores non-motile except in chytrids (asexual zoospores)
• asexual (mitotical) spores: typically called conidia
• sexual (meiotical) spores

Question 8

What are main features of Microsporidia

Answer 8

• microscopic unicellular parasites of animals, ca 1500 spp.
  
  • extremely small cells (1-5 µm)
  • mitochondria reduced to mitosomes
    
    • double membrane but no genes (genes for mitosomal components contained in the nuclear genome)
    • energy gained from host cells

Question 9

Main features of chidridmycota

Answer 9

• simply built coenocytic or unicellular fungi
• often aquatic, probably representatives of earliest diverging lineages, 750-1000 spp.
• flagellated asexual zoospores and gametes, variety of sexual modes of reproduction

Question 10

Occurance of chytrids

Answer 10

• soils, waters, animal rumens
• often plant pathogens and animal parasites

Question 11

Importance of chytrids

Answer 11

Synchytrium endobioticum – potato wart disease

• strongly infectious obligate parasite, spores viable up to 50 years
• no fungicide working
• on USA’s federal bioterrorism list for agricultural plant pathogens

Batrachochytrium dendrobatidis – amphibian chytrid fungus

•infects the keratinized skin of amphibians devastated amphibian populations worldwide after 1998

Question 12

Main features of Zygomycetes

Answer 12

non-monophyletic group of microscopis fungi, producing zygospores

• sexually-produced resting spores originating in thick-walled zygosporangia
• ca. 1000 species of fungi, forming mostly coenocytic mycelium with stolones and rhizoids
• asexual sporangia on sporangiophores
• sexual zygosporangia

Question 13

Describe the ecological diversity of Zygomycetes

Answer 13

• remarkable ecological diversity
• intestinal microflora of arthropodes
• parasites of plants, animals, other fungi, even amoebas
• ectomycorrhizal fungi (Endogone)
• saprophytic fungi – living on fruits (fermentation), earth, faeces

Question 14

Describe main features of Dikarya: ascomycetes and basidiomycetes

Answer 14

• characteristic formation of dikaryotic cells of hyphae (secondary mycelium) following the plasmogamy of mating-compatible types, karyogamy postponed

Ascomycota

• meiotic spores (ascospores) formed endogeneously, in asci (sg. ascus, Latin for sac)
• the only diploid cell = young ascus in many A.
• asexual stage in the life cycle (=anamorph) often prevailing
• many species reproducing only asexually

Basidiomycota

• apart of parasitic rusts and smuts, most basiodiomycetes form fruitbodies (basidiomas, “mushrooms”)
• exogeneous sexual spores (basidiospores) forming on club-shaped sporangia – basidia
• clamp connections formed during hyphal growth
• dolipore surrounded by parenthesome around the pores in hyphal seta

Question 15

What is the importance of Ascomycota

Answer 15

• producers of antibiotics and other medically used compounds
  
  • Penicillium chrysogenum (P. notatum): penicillin; Tolypocladium inflatum: cyclosporin (suppresses immune reactions)
• food industry uses (Penicillium roquefortii)
• pathogens:
  
  • Penicillium marneffei, Pneumocystis carinii – problematic particularly for immune-deficient persons
• bioremediation (waste cleanup)

Question 16

Importance of Basidiomycota

Answer 16

• Ecologically: vital for decaying dead organic matter, including wood and leaf litter, and thus vital for the carbon cycle
• form important symbiotic relations – ectomycorrhizas
  
  • whereby the fungus receives carbohydrates from the plant’s photosynthesisand the plant gains the mycelium’s very large surface area to absorb water and mineral nutrients from the soil
• humans: food source
• rusts and smuts are parasitic on plants and cause diseases