mycology

• Mycology


  Study of fungi
• Mycology


  • Includes research of genetic and biochemical properties and use in medicine and food
• Mykes


  Greek word for mushroom
• Agostino Bassi


  The first to demonstrate that a microorganism is the cause of a disease
• Agostino Bassi's 1808–1830 experiment


  A vegetable parasite called Calcinaccio infected silkworms and caused disease
• Calcinaccio


  Pathogenic to insects, presently known as Beauveria bassiana, named after Bassi
• Raymond Saubouraud


  • Published Les Teignes, a comprehensive study of dermatophytic fungi, in 1910
  • Father of Medical Mycology
• Fungi


  • Eukaryotic organisms with membrane-bound organelles and nucleus
  • 2 major groups: Yeast and Molds
  • Lacks chlorophyll, unable to produce own food
  • Possess a cell wall, have filamentous structures (hyphae), and produce spores
  • Grow as saprophytes and decompose dead organic matter
• Out of 100,000 to 200,000 species (depending on how they are classified), ONLY 300 species are pathogenic for man
• Fungi


  • Diameter: Approx. 4 μm (Candida)
  • Nucleus: Eukaryotic
  • Cytoplasm: WITH mitochondria and endoplasmic reticulum
  • Cell Membrane: Sterols present
  • Cell Wall Content: Chitin
  • Spores: Sexual and asexual spores for reproduction
  • Thermal: Dimorphism Yes (to some)
  • Metabolism: Require organic carbon, no obligate anaerobes
• Bacteria


  • Diameter: Approx. 1 μm (Staphylococcus)
  • Nucleus: Prokaryotic
  • Cytoplasm: NO mitochondria and endoplasmic reticulum
  • Cell Membrane: Sterols absent (except Mycoplasma)
  • Cell Wall Content: Peptidoglycan
  • Spores: Endospores for survival, not for reproduction
  • Thermal: No
  • Metabolism: Many do not require organic carbon, many obligate anaerobes
• Fungi

  • Heterotrophic
  • Use complex organic compound as source of carbon
  • Lacks chlorophyll
  • Embedded in a food source or medium
  • Obtain nourishment by secreting enzymes for external digestion and by absorbing nutrients that are released from medium
• Saprophytes


  Obtain energy from dead organic material
• Fungal metabolism

  1. Secretes hydrolytic enzymes to break down external substances

  2. Absorb nutrients released from medium to produce energy
• Hydrolytic enzymes


  • Cellulase
  • Protease
  • Keratinase - breaks down keratin leading to fungal infections in the skin
• Growth requirements


  • Obligate aerobes - require oxygen and moisture
  • Temperature range: 0-60°C, Optimum: 25-30°C
  • Can grow in wide range of pH: 1-12, Optimum: 7
• Refrigerator temperature is 2-8°C allowing molds to still grow on refrigerated food
• Fungal infections in the feet


  • Due to overgrowth of organisms while wearing socks
• Growth of most yeast take several days while bacterias are fast growers
• Fungi of medical importance can take several weeks to form visible colonies
• Asexual reproduction


  1. Anamorph (reproductive elements are called conidia)

  2. Individual produces genetic copy of the parent without help of another individual

  3. Involves mitotic division of haploid nucleus

  4. Associated with production by budding spore like conidia or by separation of hyphal elements
• Fragmentation


  • Most basic form of reproduction
  • Single-celled fungi undergoes simple division or fission, creating 2 daughter cells
  • Daughter cells undergo nuclear division and population of new cells arise
• Budding


  • Bud forms on the surface (bud cytoplasm being continuous with parent cell's cytoplasm)
  • Parent cell's nucleus splits and one migrates to the bud while the other remain
  • The parent cell can produce numerous buds over its surface by continuously synthesizing cytoplasm and repeating nuclear divisions
  • Such individual buds will pinch off and form filamentous fungus hyphae that act like spores
  • Forms germ tube structure which goes to new hypha leading to germination
• Sporangiospores


  Asexual spores generated in sporangia (sac-like structure)
• Sporangium formation

  Formed at the end of the sporangiophore (peculiar aerial hyphae)
• Sporangium


  Contains a high number of haploid spores that are discharged when the sporangial wall is ripped open
• Sporangiospores

  • Rhizopus
• Conidiospores


  Conidia are single-celled or multicellular structures that emerge from the tip or side of the aerial hyphal structure known as the conidiophore (stalk-like structure)
• Conidiospores


  May be solitary or in groups
• Conidiospores


  • Penicillium
  • Aspergillus
• Arthrospores


  • Primitive type
  • Formed by the breaking of fungal mycelium
  • Formed by separation followed by fragmentation of hyphae
• Arthrospores

  • Trichosporon
  • Geotrichum
  • Coccidioides
• Chlamydospores


  • Usually formed during unfavorable conditions
  • Thick-walled single-celled spores, which are highly resistant to adverse conditions
  • Swelling before spores are released
  • Hyphal cell or portion of the hyphae contracts, loose water, round up and develops into thick-walled chlamydospores
  • When favorable conditions return, chlamydospores give rise to new individual fungi
• Blastospores


  • Budding spores formed at the terminal end of the hyphae (looks like a flower)
  • Spores may remain attached to hyphae and bud further to give branching chain of blastospores
• Blastospores


  • Ascomycetes
  • Zygomycetes
  • Basidiomycetes
• Teleomorph


  • Carried out by diffusion of compatible nuclei from two parent at a definite state in the life cycle of fungi
  • Three phases: Plasmogamy - fusion of protoplasm, Karyogamy - fusion of nucleus, Meiosis - reductional nuclear division
• Sexual spores produced due to sexual reproduction

  • Ascospores
  • Basidiospores
  • Zygospores
  • Oospores
• Sexual spores are fewer in number than asexual spores
• Basic structures of fungi

  • Unicellular yeast cells with budding
  • Multicellular, filamentous molds
• Yeast


  Grow in a round circular forms, unicellular, reproduce by budding