Wk13, 1st lecture

• Fungi


  Eukaryotes that are morphologically and ecologically diverse, can be unicellular or multicellular, made of hyphae, reproduce via spores, closer related to animals than to plants, encompass six phyla spanning one billion years of evolution, and cause a large diverse range of human infections
• Fungi


  • Cell wall contains chitin (cellulose in plants)
  • Cell membrane - major sterol is ergosterol (cholesterol in animals)
  • Bodies made of elongated filaments
  • Sexual and asexual reproduction
  • Reproduce via spores
  • Heterotrophic - cannot produce their own food, like plants
  • Osmotrophic - uptake of dissolved organic compounds by osmosis
  • Chemoorganotroph - organisms that oxidise the chemical bonds in organic compounds as their energy source
• Fungi are older than dinosaurs

  500 million years
• Fungi were the first to colonise the land masses
• Fungi play important roles in soil generation, nutrient transport/transformation, and the nitrogen cycle
• Major fungal phyla


  • Basidiomycota
  • Ascomycota
  • Glomeromycota
  • Zygomycota
  • Chytridiomycota
  • Cryptomycota
• Basidiomycota (club fungi)


  • 30,000 described species, incl. mushrooms
  • Unicellular or multicellular
  • Sexual or asexual
  • Terrestrial or aquatic
  • Diagnostic feature - basidia
• Ascomycota (cup fungi)


  • 75% of all described fungi
  • Unicellular or multicellular
  • Sexual or asexual
  • Some combine with algae to form lichens
  • Moulds produce potent carcinogens (aflatoxins)
  • Diagnostic feature - ascus
• Glomeromycota (mycorrhizal fungi)


  • 150 described species
  • Obligate symbionts
  • Form highly branched structures for nutrient exchange called arbuscules
  • No genetic recombination
  • Diagnostic feature - spore morphology
• Zygomycota (pin moulds)


  • 1,050 described species
  • Pathogens, plant mutualists, decomposers
  • Terrestrial and aquatic
  • Diagnostic feature - zygospores
• Chytridiomycota (basal fungi)


  • 750 described species
  • Obligate aquatic
  • Form motile asexual spores that use flagellum
  • Live as parasites or decomposers of organic matter
  • Do not produce hyphae - often reduced to single cell
  • Diagnostic feature - zoospores
• Cryptomycota (hidden fungi)

  • One genus - Rozella
  • Highly reduced morphology
  • Endoparasitic
  • Lost their 'dinner jacket' - no chitin in cell wall when absorbing food
• Teleomorph


  Sexual fungal life cycle stage
• Anamorph


  Asexual fungal life cycle stage
• Fungi kill as many people as malaria or TB
• Mould


  Hyaline moulds (e.g. Aspergillus fumigatus, Rhizopus oryzae) and dimorphic environmental moulds (e.g. Blastomyces dermatitis, Coccidioides immitis, Histoplasma capsulatum, Paracoccidioides brasiliensis, Penicillium marneffi)
• Primary pathogens


  Cause damage in the setting of appropriate immune responses, can cause damage in normal hosts
• Opportunistic pathogens


  Associated with disease only in individuals with impaired immune function, almost never cause symptomatic or clinically apparent infections in individuals with normal immunity
• Fungal infections are difficult to treat due to paucity of suitable drug targets, poor and invasive diagnostics, emergence of drug resistance, and fungi being part of the microbiome