SYSTEMATICA LECTURE

• Fungi


  • Diverse and widespread
  • Essential for the well-being of most terrestrial ecosystems by breaking down organic material and recycling vital nutrients
  • About 100,000 species have been described
  • Estimated 1.5 million species
• Fungi


  Heterotrophs that feed by absorption
• Fungi


  • Use enzymes to break down a large variety of complex molecules into smaller organic compounds
  • Exhibit diverse lifestyles (decomposers, parasites, mutualists)
• Fungal body structure


  • Most common are multicellular filaments and single cells (yeasts)
  • Some species grow as either filaments or yeasts; others grow as both
  • Morphology of multicellular fungi enhances their ability to absorb nutrients
• Mycelium


  Networks of branched hyphae adapted for absorption
• Fungal cell walls


  • Contain chitin
• Hyphae


  • Most have hyphae divided into cells by septa, with pores allowing cell-to-cell movement of organelles
  • Coenocytic fungi lack septa and have a continuous cytoplasmic mass with hundreds or thousands of nuclei
• Specialized hyphae in mycorrhizal fungi


  • Haustoria allow them to penetrate the tissues of their host
• Mycorrhizae


  Mutually beneficial relationships between fungi and plant roots

  
• Ectomycorrhizal fungi


  • Form sheaths of hyphae over a root and also grow into the extracellular spaces of the root cortex
• Arbuscular mycorrhizal fungi


  • Extend hyphae through the cell walls of root cells and into tubes formed by invagination of the root cell membrane
• Mycorrhizal fungi


  Deliver phosphate ions and minerals to plants
• Fungi and animals are more closely related to each other than they are to plants or other eukaryotes
• Fungi, animals, and their protistan relatives form the opisthokonts clade
• Major fungal divisions


  • Chytrids (1,000 species)
  • Zygomycetes (1,000 species)
  • Glomeromycetes (160 species)
  • Ascomycetes (65,000 species)
  • Basidiomycetes (30,000 species)
• Fungal classification


  • Division Myxomycophyta (Slime Molds)
  • Division Eumycophyta (True Fungi)
  • Class Phycomycetes
  • Class Ascomycetes
  • Class Basidiomycetes
  • Class Deuteromycetes

  
• Division Myxomycophyta (Slime Molds)

  • Vegetative body consists of only protoplast bounded by membrane and devoid of cell wall
  • Phagotropic mode of nutrition
  • Reproduce by spore within sporangia

  
• Classes of Division Myxomycophyta


  • Acrasiomycetes
  • Hydromyxomycetes
  • Myxomycetes
  • Plasmodiophoromycetes
• Class Acrasiomycetes (Amoeboid Slime Molds)


  • Somatic phase- amoeboid cells/myxamoebae
  • Myxamoebae form pseudoplasmodium fruiting body
  • Spore wall with cellulose
  • Sexual and Asexual Reproduction
  • Lack flagellated cells

  
• Class Hydromyxomycetes


  • Aquatic & Saprophytic
  • Thallus with uninucleate spindle shaped cells forming extensive filaments (net plasmodium)
  • Reproduction- cyst or zoospore formation, or congregation

  
• Class Myxomycetes (True/Plasmodial Slime Mold)

  • Vegetative body- free-living plasmodium
  • Sexual and Asexual reproduction
  • Asexual reproduction- fragmentation of plasmodium or binary fission in myxamoebae

  
• Class Plasmodiophormycetes (Endo-parasitic Slime Molds)


  • Obligate parasite; grow on algae, aquatic fungi and higher plants
  • Somatic body- necked holocarpic plasmodium
  • 2 types of life cycles: Sporangiogenous plasmodium from sporangia, Cytogenous plasmodium gives rise to cyst

  
• Class Plasmodiophormycetes


  • Plasmodiophora- causing clubroot of crucifers
  • Polymyxa- root disease of cereals and grasses
  • Spongospora- causing the powdery scab of potato
• Class Phycomycetes


  • Exhibit great diversity of life histories
  • Include fast-growing molds, parasites, and commensal symbionts
  • Hyphae are coenocytic
  • Asexual sporangia produce haploid spores

  
• Zygomycetes


  • Named for their sexually produced zygosporangia
  • Zygosporangia are the site of karyogamy and then meiosis

  
• Myxomycophyta (Slime Molds)


  • Damp places, old wood, decomposing plant parts
  • Obligate parasite; grow on algae, aquatic fungi and higher plants
  • Somatic body- necked holocarpic plasmodium

  
• Life cycles of Myxomycophyta

  1. Sporangiogenous plasmodium- from sporangia

  2. Cytogenous plasmodium- gives rise to cyst
• Plasmodiophora


  Causing clubroot of crucifers
• Polymyxa


  Root disease of cereals and grasses
• Spongospora


  Causing the powdery scab of potato
• Phycomycetes


  • Fast-growing molds, parasites, and commensal symbionts
  • Hyphae are coenocytic
  • Asexual sporangia produce haploid spores

  
• Life cycle of Rhizopus stolonifer (black bread mold)

  1. Mating type (-) and (+) gametangia with haploid nuclei

  2. Plasmogamy

  3. Karyogamy

  4. Meiosis

  5. Asexual reproduction via sporangia

  6. Dispersal and germination
• Phycomycetes genera


  • Saprolegnia (water molds)
  • Rhizopus (Bread molds)
  • Mucor (PinMold)
  • Albugo (White Rust)
  • Pythium
• Ascomycetes


  • Produce sexual spores in saclike asci contained in fruiting bodies called ascocarps
  • Vary in size and complexity from unicellular yeasts to elaborate cup fungi and morels

  
• Life cycle of Neurospora crassa (ascomycete)

  1. Mating type (-) and (+) conidia

  2. Plasmogamy

  3. Karyogamy

  4. Meiosis

  5. Asexual reproduction via conidia

  6. Sexual reproduction via ascocarps and asci

  7. Dispersal and germination
• Ascomycetes genera


  • Yeast (Saccharomyces cerevisiae)
  • Aspergillus (Black Mold)
  • Penicillium
  • Neurospora (Nerve Spore)
  • Peziza (Violet cup fungus)

  
• Basidiomycetes


  • Include mushrooms, puffballs, and shelf fungi, mycorrhizae, and plant parasites
  • Defined by a clublike structure called a basidium, a transient diploid stage in the life cycle
  • Many are decomposers of wood
• Life cycle of a mushroom-forming basidiomycete


  1. Mating type (-) and (+) haploid mycelia

  2. Plasmogamy

  3. Karyogamy

  4. Meiosis

  5. Basidiospore formation and dispersal

  6. Germination

  
• Basidiomycetes genera


  • Agaricus (button Mushroom)
  • Polysporus (ping-pong bat)
  • Puccinia (Rust Fungus)
  • Ustilago (corn smut)
  • Lycoperdon
• Deuteromycetes (Imperfect Fungi)


  • Saprophytes and parasites
  • Unicellular and Multicellular
  • Asexual reproduction by spores
  • Parasexual cycle