Bio 117: Food Microbiology

• Characteristics of Algae:

  • Algae are relatively simple eukaryotic photoautotrophs that lack the tissues of plants
  • Most algae are aquatic and mostly found in the ocean
  • Algae require water for physical support, reproduction, and nutrient diffusion
• Vegetative Structures:

  • Thallus: the body of a multicellular alga
  • Thalli of larger multicellular algae consist of holdfasts, shapes, and blades
  • Pneumatocyst: a floating, gas-filled bladder that buoys some algae
• Life Cycle:

  • Algae can reproduce asexually through fragmentation
  • Unicellular algae divide through mitosis and cytokinesis
  • Some algae can reproduce sexually, alternating between asexual and sexual reproduction
• Nutrition:

  • Algae are photoautotrophs found throughout the photic (light) zone of bodies of water
• • Produce neurotoxins like brevetoxins and saxitoxins
• Selected Phyla of Algae:

  1. Brown Algae (or kelp):

  • Macroscopic; some reach lengths of 50m
  • Used in the production of algin and various non-food goods

  2. Red Algae:

  • Delicately branched thalli; can live at greater ocean depths
  • Used to extract agar and carrageenan

  3. Green Algae:

  • Have cellulose cell walls, contain chlorophyll a and b, and store starch

  4. Diatom:

  • Unicellular or filamentous algae with complex cell walls
  • Store energy captured through photosynthesis in the form of oil

  5. Dinoflagellates:

  • Unicellular algae collectively called plankton
• Roles of Algae in Nature:

  • Algae fix CO2 into organic molecules consumed by chemoheterotrophs in aquatic food chains
  • Algae produce 80% of the Earth's O2 through photosynthesis
  • Algal blooms can indicate pollution in water bodies
  • Petroleum was formed from diatoms and other planktonic organisms
  • Many unicellular algae are symbionts in animals, providing essential nutrients
• the body of a multicelluar alga

  Thallus
• branched; anchor the alga to the substrate

  holdfasts
• stemlike and often hollow that connects the blade to the holdfasts

  stipes