FOM

• What is fungi?

  • Eukaryotes
  • heterotrophic (can't make own food)
  • saprophytic- feed on dead / decomposing

  matter.

  • absorptive nutrition- take in small, organic molecules + secrete digestive enzymes to break down complex molecules.
• What is the structure of fungi?

  • Entire body / structure= thallus
  • fruiting body contains hyphae that branch into the mycelium.
  • chitin cell wall for extra strength + facilitates absorption.
• Describe the structure of hyphae.

  1. Can be separated into single cellular compartments w/ 1 nucleus via a septum.
  2. Can be aseptate w/ no division so multinucleate.

  • provide moulds w/ large SA for absorption.
  • since fungi are non-mobile, hyphae grow @ tip allowing infiltration of new environments
• Fungal reproduction.

  • Most species have both sexual + asexual reproductive cycles.
  • species w/ sexual cycle= isogamous.
  • mating types '+’ and '-’
  • homothallic= same mating type can have sex.
  • heterothallic = different mating type can have

  sex.
• What are fungal spores?

  • single celled biological entities that allow fungi to

  reproduce.

  • if Asexual= dispersal purposes + product of

  mitosis.

  • Haploid
  • if land in favourable environment they germinate + produce new mycelium.
• Fungal asexual reproduction

  • Mitosis
  • Spores
  • fission (single celled yeast)
  • budding (single celled yeast)
  • fragmentation of hyphae (mould)
• Fungi sexual reproduction

  • Isogamous
  • Homothallic
  • heterothallic
  • meiosis
  • 1.Cytoplasmic fusion (plasmogamy) of + and - produce haploid dikaryon -dikaryotic stage is temporary.
  • 2. Nuclear fusion (karyogamy) - 2 nuclei fuse to produce a 1 diploid nucleus zygote.
  • 3. Meiosis produces spores
  • 4.Haploid spores released + new mycelium produced.
• What are the 6 major fungal phyla?

  1. chytridiomycota
  2. zygomycota
  3. Glomeromycota
  4. Ascomycota
  5. Basidiomycota
  6. microsporidia
• Glomeromycota

  • Large, multinucleate BLASTOSPORES produced by budding.
  • endomycorrhizal = penetrates plant roots.
• Basidiomycota

  • Fruiting body w/ basidia.
  • sexual basidiospores produced externally.
  • eg mushrooms
• Ascomycota

  • ASCOCARP fruiting body (cup shape)
  • sexual ASCOSPORES internally in sacs- ASCI.
  • asexual CONIDIOSPORE on tip of multicellular mould hypha.
  • some are edible, research tools, pathogens + can cause food spoilage.
  • eg orange peel fungus.
• Zygomycota

  • sexual reproduction of diploid ZYGOSPORES under stress.
  • spores dormant until favourable conditions, then meiosis.
  • eg Mucor bread mould.
• Chytridiomycota

  • Sexual + asexual reproduction.
  • FLAGELLATED, motile sexual ZOOSPORES.
• Microsporídia

  • Intracellular parasites.
  • Sexual + asexual reproduction.
• Saccharomyces cerevisiae life cycle

  • Alternates b/n diploid (preferred) + haploid.
  • Favorable environment= asexual reproduction = mitosis via budding (leaves scars).
  • unfavourable environment= sexual reproduction -> heterothallic: a + alpha.
  • if a + alpha are close enough they mate to produce diploid cell.
  • haploid cells can also switch mating types if not close to cells of opposite type. Eg a can find another a but not alpha- it switches to alpha.
• Saccharomyces cerevisiae life cycle (2)

  1. Favorable conditions diploid state - asexual reproduction by budding.
  2. Unfavourable conditions - cells undergo meiosis to produce haploid stress tolerant ascopores (housed in ascus).
  3. Spores (a and alpha) released when environment is stable again + can reproduce asexually.
  4. When spores of opposite mating type Meet, they mate to produce favoured diploid state. (Cycle repeats)
• Saccharomyces cerevisiae mating

  • 2 types: a + alpha.
  • each have its own pheromones + receptor for pheromone of opposite mating type.
  • close enough together = shmoo forms.
  • cell fuse + nuclei fuse.
  • divide by mitosis forming diploid daughter by budding
• Ascomycota filamentous life cycle

  1. '+'/'antherium' and '-'/ 'ascogonium' types grow closer due to pheromones.
  2. Cytoplasmic fusion produces dikaryon hyphae that grows from ascogonium.
  3. Dikaryon hyphae grow forming cup-like ascocarp
  4. Karyogamy inside ascus.
  5. Meiosis
  6. Mitosis
  7. Fully formed ascus w/ 8 spores.
• Microsporidia unique structure

  1. external surface = endospore of chitin.
  2. Posterior vacuole w/ catalase activity.
  3. Polar filament + anchoring disc for host invasion.
• Microsporidian life cycle

  1. spore ingested by host- germinates + releases intracellular polar filament.
  2. Injects polar filament into host cell.
  3. Releases sporoplasm inside host cell.
  4. Sporoplasm becomes 'meronts' - cells W/ loosely organised organelles enclosed in simple plasma membrane.
  5. Meronts divide (sporogony) + form sporoblasts, building up thick exospore layers- mature spores.
  6. Mature spores completely fill host cell + puncture plasma membrane.
  7. Spores released into surroundings to infect neighbouring cells.
• What are 2 microsporidian human infections?

  1. Enterocystozoon bieneusi
  2. Encephalitozoon cuniculi
• What are the 2 main types of human fungal pathogens?

  1. Commensals - normal components of human microbiome = opportunistic.
  2. Environmental- In specific environmental niches. Humans become exposed by inhaling, infesting spores/ yeast cells. Some can be opportunistic.
• What virulent traits do fungi have?

  1. Optimal growth @ 37 °C.
  2. Dimorphic yeast to Mould transition.
• What are the 5 classifications of fungal diseases?

  1. Superficial mycoses
  2. Cutaneous
  3. Subcutaneous
  4. Systemic- infection in visceral (internal) tissue
  5. opportunistic- non pathogenic organisms turned pathogenic when Immune system compromised.
• Name 3 fungal infections, their mode of infection + phyla.

  1. Subcutaneous = PHIALOPHORA VERRUCOSA =ASCOMYCOTA -infects legs + feet
  2. Systemic = CRYPTOCOCCUS NEOFORMANS =BASIDIOMYCOTA - infects lungs, bones, CNS.
  3. opportunistic= ENCEPHALITOZOON = MICROSPORIDIA- infects lungs, brain.
• Candidiasis

  • Opportunistic
  • caused by dimorphic candida yeast.
  • effects skin, mucous membranes of tissues, bloodstream.
  • candida species form biofilms of dense ECM secreted by the yeast - forms on solid surfaces.
  • ECM environment promotes v-m transition.
• Candida biofilms

  • Protective layer around candida.
  • drug resistance
  • Can form inside the body, protecting candida from host immune system.
• Anti-fungal therapies

  • Target a fungal specific protein/ cellular structure.
  • fungistatic = stops fungus dividing. (Mostly used).
  • fungicidial = kills fungal cell. - targets membrane, cell wall, intracellular.
• Examples of fungal plant pathogens

  1. Rye ergot = claviceps purpurea
  2. Banana fungal disease/ Panama disease= fusarium oxysporum.
• Claviceps purpurea life cycle

  • Sexual + asexual

  1. Ergots remain on rye in winter months.
  2. Ergots fall to ground + germinate in spring + hyphae mate forming dikaryotic hyphae.
  3. Fruiting body forms w/ developing asci.
  4. Ascopores released into air + land on new plant.

  Asexual= conidiospores- fungus produces honeydew sticky liquid

  That attaches conidiospores to insects to be spread.