fungi and yeast

• Fungi


  Organisms that are a little bit like plants, and more like animals than you might think
• Fungi diverged from protists about a billion years ago
• Scientists estimate there are about 1.5 million species of Fungi on the earth, though we only know about 100,000 or so of them
• Types of fungi


  • Fun fungi (like yeast)
  • Fungi that cause diseases (like athlete's foot, histoplasmosis, and ergot poisoning)
  • Fungi that threaten other animals (like white nose syndrome in bats and fungal diseases in amphibians)
• Fungi's vital function


  They feast on the deceased remains of almost all organisms on the planet, converting organic matter back into soil from which new life will spring
• Beer had been brewed for thousands of years before Pasteur's time, but no one understood how its most important ingredient (yeast) worked
• Pasteur's discovery about yeast


  1. Yeast are living organisms

  2. In the absence of free oxygen, yeast can obtain energy by decomposing substances that contained oxygen (anaerobic respiration/fermentation)

  3. Beer was often contaminated by other bacteria and fungi, which could be thwarted by heating the beer (pasteurization)
• Heterotrophs


  Fungi, like us, absorb nutrition from their surroundings instead of eating
• Fungi


  • They secrete powerful enzymes that break down complex molecules into smaller organic compounds, which they use to feed, grow, and reproduce
  • Their cell walls are strengthened by chitin, the same material found in insect exoskeletons
  • Their hyphae and mycelium are structured to maximize surface area for absorbing nutrients
• Ways fungi interact with other organisms


  • Decomposers
  • Mutualists (like mycorrhizal fungi that help plants absorb nutrients)
  • Predators
  • Parasites (like the zombie ant fungus)
• Fungal reproduction


  1. Asexual reproduction (producing spores)

  2. Sexual reproduction (involving mating types, plasmogamy, and spore production)

  3. Asexual reproduction in unicellular yeasts (cell division, budding)
• Yeast's role in beer production is to convert sugars into alcohol, carbon dioxide, and flavors