algae

1. COURSE :B.SC. (MICRO)
SUBJECT: ELEMENTARY MICROBIOLOGY
UNIT 3.2
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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
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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)
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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.
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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.
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7. Comparison of Algae and Plant Structure
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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.
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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.
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10. Euglenoids are Flagellated, Unicellular Algae
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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
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12. 12
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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
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15. Whiplike flagellum
“Hairy” flagellum
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16. Pneumocyst
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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).
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19. Lichens: Combinations of Fungi and Green Algae (or
Cyanobacterium)
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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.
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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.
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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.
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