Fungi

• Fungi are eukaryotes and are represented mostly by filamentous (true hyphae) but some are unicellular (yeast).
• All fungi are chemoheterotrophs which means they use inorganic molecules as source of energy (oxidize H2, H2S, Fe2S, NH4+) and organic compounds as source of carbons (glucose).
• Fungi are capable of sexual and asexual reproduction.
• Asexual reproduction in Fungi is more important for propagation because:

  1. Results in the production of numerous individuals
  2. Repeated several times during the season
• (Topic: Method of Asexual Reproduction)

  Asexually, fungi can reproduce by fragmentation by hyphae breaking up into component cells. These component cells behave as spores called arthrospores.
• (Topic: Method of Asexual Reproduction)

  Asexually, fungi can reproduce by fission by the simple splitting of a cell into 2 daughter cells by the formation of cell wall.
• (Topic: Method of Asexual Reproduction)

  Asexually, fungi can reproduce by budding via the production of small outgrowth from parent cell.
• (Topic: Method of Asexual Reproduction)

  Asexually, fungi can reproduce by spores which is the most common method.
• (Topic: Method of Asexual Reproduction)

  Zygomycetes, Chytridiomycetes, and Oomycetes have a sporangiophore. At the free end of the sporangiophore is a sporangia (sac-like structures) that produce 50,000 sporangiospores.
• (Topic: Method of Asexual Reproduction)

  Ascomycetes like Aspergillus and Penicillium have conidiophores that have conidia also called conidiospores (NOT sac-like) at the free end. Conidia are haploid cells that are identical to the haploid parent.
• Mycorrhizae is the symbiotic association between plant roots and fungi.
• 2 types of Mycorrhizae:

  1. Ectomycorrhizae - fungal hyphae form a sheath around the root and extend into soil => increases surface area for absorption
  2. Endomycorrhizae or arbuscular mycorrhizae - fungal hyphae penetrate the root cells => facilitate the exchange of phosphorus and nitrogen (common in agricultural crops)
• Chitin is the polymer of N-acetylglucosamine (NAG) in the cell wall of fungal cells.
• Appendage of parasitic fungus that penetrates the host's tissue to draw nutrients is called haustoria.
• Arbuscle is a structure within the root cell that is the site of nutrient transfer between fungi and plant.
• Hartig Net is the network of ectomycorrhizal hyphae where nutrient exchange occurs.
• Members of Glomeromycetes are mutualistic symbionts that form arbuscular mycorrhizae (or endomycorrhizae) within plant root cells.
• (Topic: Method of Sexual Reproduction)

  Three phases:

  1. Plasmogamy - the union of 2 protoplasts bringing nuclei together within the same cell
  2. Karyogamy - fusion of 2 nuclei brought together by plasmogamy
  3. Meiosis - reduction of chromosomes to haploid
• (Topic: Method of Sexual Reproduction)

  Types:

  1. Planogametic copulation - protoplasts of gametes of complementary mating types fuse
  2. Somatogamy - fusion of protoplasts of somatic cells
  3. Spermatization - fusion of hyphal tips
• Zygomycetes produce sporangiospores and obtain nutrients from decaying matter.
• Chytridiomycetes are a group that retained most ancient features such as flagellated spores.
• Ascomycetes produce conidiospores or conidia and are the largest and most diverse group.
• Basidiomycetes are a group that forms mushrooms. They have a basidia where haploid basidiospores are formed via meiosis.
• Examples of fungi belonging to Basidiomycota are toadstools, puff-balls, smuts, and rusts.
• Nonmotile sporangiospores are called aplanospores. They rely on passive transport by water currents.
• Zoospores lack true cell walls and bear 1 or more flagella; can swim to a favorable environment.
• Conidia or conidiospores (asexual) grow on tips of aerial hyphae called conidiophores giving a dusty appearance. (Division Ascomycota)
• Blastospores or blastoconidium (asexual) are produced from a budding parent cell. (Division Glomeromycota)
• Arthrospores (asexual) are produced from fragmentation of hyphae breaking into component cells that behave as spores. Arthrospores are NOT TRUE spore, primitive but nonmotile.
• Mycoses that extend deeper into the epidermis such as invasive hair and nail diseases are called cutaneous.
• Cutaneous mycoses infect the stratum corneum (outer layer) such as hair and nails.
• Opportunistic mycoses infect immunosuppressed patients but do not affect healthy individuals.
• Superficial mycoses are infections localized on the surface of epidermal cells along the hair shafts.
• Systemic mycoses are infections found deep within the body, not restricted in any region or organ.
• Saprophytes grow on decomposing organic matter and take up non-living organic nutrients in dissolved form.
• In order, what are the three stages of sexual reproduction in fungi?

  1. Plasmogamy
  2. Karyogamy
  3. Meiosis
• Lichens are a symbiotic relationship between a fungus and an alga.
• The reproductive structures of lichens are called soredia.
• Lichens are small, asexual propagules composed of clusters of fungal hyphae intertwined with algal or cyanobacterial cells.
• The outgrowth of somatic hyphae in parasitic fungi for nutrient absorption is haustoria.