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B.sc. (micro) i em unit 3.2 algae

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B.sc. (micro) i em unit 3.2 algae

  1. 1. COURSE :B.SC. (MICRO) SUBJECT: ELEMENTARY MICROBIOLOGY UNIT 3.2 1
  2. 2. Algae  Simple, eukaryotic phototrophs that carry out oxygenic photosynthesis using chlorophyll a  Have sexual reproductive structures  Every cell becomes a gamete  Differ widely in distribution, morphology, reproduction, and biochemical traits © 2012 Pearson Education Inc. 2
  3. 3. Algae  Distribution of Algae  Most are aquatic  Live in the photic zone of fresh, brackish, and saltwater  Accessory photosynthetic pigments that trap energy of light and pass it to chlorophyll a  Morphology of Algae  Unicellular, colonial, or have simple multicellular bodies (thalli) © 2012 Pearson Education Inc. 3
  4. 4. II. ALGAE Vegetative Structures of multicellular algae:  Thallus: Body. Lacks conductive tissue.  Holdfasts: Anchor alga to rock.  Stipes: Hollow, stem-like structures. Does not support weight.  Blades: Leaf-like structures.  Pneumatocyst: Floating, gas-filled bladder. DIVISIONS OF ALGAE Green algae: May be unicellular or multicellular.  Have cellulose cell walls, contain chlorophyll a and b, and store starch like plants. Most are microscopic. Live close to water surface. Believed to be the ancestors of terrestrial plants.  Sexual & Asexual production. 4
  5. 5. 5 1
  6. 6. Brown Algae or Kelp: Macroscopic (up to 50 m long). Most are found in coastal waters, at intermediate depths. Rapid growth. Can be harvested regularly. Red Algae: Live at greater ocean depths than other algae. Red pigments allow them to absorb blue light that penetrates deepest into ocean. Agar is extracted from many red algae. Some produce lethal toxins. 6
  7. 7. Comparison of Algae and Plant Structure 7 2
  8. 8. DIVISIONS OF ALGAE (Continued)  Diatoms: Unicellular or filamentous algae with complex cell walls with silica or calcium.  Two parts of cell wall fit together like Petri dish. Distinctive patterns are used for identification. Store energy in form of oil.  Some diatoms can cause neurological disease (memory loss and diarrhea) in people who eat mussels, due to domoic acid intoxication.  Fossil deposits of diatoms (diatomaceous earth) are used as filtering agents and abrasives in several industries. 8
  9. 9. Dinoflagellates (Plankton): Unicellular free-floating algae. Rigid structure due to cellulose in plasma membrane.  Some dinoflagellates produce neurotoxins, which kill fish, marine mammals, and humans.  Paralytic shellfish poisoning: Consumption of clams and mussels that have eaten dinoflagellates (Gonyaulax) that produce neurotoxin.  Red Tide: Caused by large concentrations of (Gonyaulax). Euglenoids: Unicellular, flagellated algae. Semi-rigid plasma membrane (pellicle). Most have anterior red eye spot. Frequently studied with protozoa, because lack a cell wall. 9
  10. 10. Euglenoids are Flagellated, Unicellular Algae 10 3
  11. 11.  Reproduction in Algae  Unicellular algae  Asexual reproduction involves mitosis followed by cytokinesis  Sexual reproduction forms zygotes from individual gametes  Zygote undergoes meiosis  Multicellular algae  Reproduce asexually by fragmentation  Reproduce sexually with alternation of generations © 2012 Pearson Education Inc. 11
  12. 12. 12 4
  13. 13. Male haploid individual Female haploid individual Female gamete Male gamete Fusion Zygote Diploid individual Meiosis Male and female haploid spores Diploid (2n) generation Haploid (1n) generation 13 5
  14. 14. 14 6
  15. 15. Whiplike flagellum “Hairy” flagellum 15 7
  16. 16. Pneumocyst 16 8
  17. 17. 17 9
  18. 18. LICHENS Combination of a green alga (or cyanobacterium) and a fungus. Mutualistic relationship in which each partner benefits.  Alga: Provides nutrients by photosynthesis to fungus.  Fungus: Provides attachment and protection from desiccation. 20,000 species of lichens occupy unique habitats, in which either fungi or algae could not survive alone: rocks, cement, rooftops, trees, and newly exposed soil. Grow very slowly, secreting acids that break down rocks. Accumulate nutrients needed for plant growth. Sensitive to air pollution. Major food source for tundra herbivores (caribou and reindeer). 18
  19. 19. Lichens: Combinations of Fungi and Green Algae (or Cyanobacterium) 19 10
  20. 20. 20 11
  21. 21. Ecological Importance of Algae Important part of the food chain in aquatic ecosystems because they fix carbon dioxide into organic molecules that can be used by heterotrophs. 80% of the earth’s oxygen is believed to be produced by planktonic algae. Algal blooms are indicators of water pollution.  Grow rapidly in water with high concentrations of organic material (sewage or industrial waste). Petroleum and natural gas reserves were formed primarily from diatoms and plankton. Many unicellular algae are symbionts in animals. 21
  22. 22. IV. SLIME MOLDS Have both fungal and animal characteristics.  Amoeboid stage  Produce spores like fungi Eukaryotic, classified as protists. Cellular and plasmodial (acellular) slime molds. Life Cycle of Cellular Slime Molds:  Amoeba stage: Germinate from a spore.  Slug stage: Many amoebas aggregate and sheath forms. Migration.  Fruiting body: Releases spores which germinate into amoebas. Plasmodial (Acellular) Slime Molds  Mass of protoplasm with many nuclei (plasmodium).  Capable of sexual reproduction. 22
  23. 23. Reference:  Images (1 to 11): 1. Microbiology by Gerard J. Tortora, Christine L Case, and Berdell R. Funke 2. Brock Biology of Microorganisms (13th Edition) by Michael T. Madigan, John M. Martinko, David Stahl. 23

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