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Photosynthetic Prokaryotes Chapter 13

Photosynthetic Prokaryotes Chapter 13. Kingdom - Bacteria Phylum- Cyanobacteria. Cyanobacteria- Gram Negative Bacteria. Gram positive - peptidoglycan layer; stains with crystal violet.

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Photosynthetic Prokaryotes Chapter 13

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  1. Photosynthetic ProkaryotesChapter 13 • Kingdom- Bacteria • Phylum- Cyanobacteria

  2. Cyanobacteria- Gram Negative Bacteria • Gram positive- peptidoglycan layer; stains with crystal violet. • Gram negative- peptidoglycan layer sandwiched by lipopolysaccharide and protein layers; does not stain with crystal violet.

  3. Cyanobacteria • Characteristics • Chlorophyll A • Phycobilisomes • Thylakoids occur singly • 70s ribosomes • DNA microfibrils central • Polyhedral bodies • Gas vesicles • Habitat- ubiquitous. • Examples- Anabaena, Nostoc, Oscillatoria, Lyngbya, Synechococcus, Synechocystis.

  4. Habits • Unicells • Singly- Synechocystis • Colonies of unicells- Aphanothece • Rows of cells • Unbranched filaments w/out sheath (trichome)- Oscillatoria • Many trichomes in 1 large sheath- Microcoleus • Unbranched filaments with sheath- Lyngbya • Uniseriate branched filaments- Mastigocladus • Multiseriate branched filaments- Stigonema • Pseudo-branched filaments- Scytonema

  5. Asexual Reproduction • Endospores- internal division of the protoplast results in a mass of spores. • Fragmentation- filament breaks into 2 parts, each of which forms a new thallus. • Hormogonia- short sections of a trichome detach and form a new thallus. • Akinetes- resting spores; cells that are resistant to unfavorable conditions. • Binary Fission- division of a single-celled individual into two new single-celled individuals.

  6. Heterocyst • Heterocyst- a thick-walled large cell that fixes atmospheric nitrogen (diazotroph). • Photosynthetically inactive. • Their formation is inversely related to nitrogen concentration. • Microplasmodesmata- cytoplasmic connections that transfer metabolites and ammonium.

  7. Movement in the Cyanobacteria • Gliding- active movement of an organism in contact with a solid substrate. • Mechanism- mucilaginous layer of microfibrils generates waves. • Swimming- active movement of an organism without contact with a substrate. • Mechanism- unknown. • Why? • Positively phototactic- dim light. • Positively chemotactic- nutrients.

  8. Symbiotic Associations • Lichens- cyanobacteria occur in about 8% of the species. • Azolla- the water fern; contains Anabaena in the dorsal lobe of its leaf. • Colonial ascidian- sea squirt. • Amoeba, protozoa, diatoms, green algae, mosses, liverworts, water molds, and vascular plants.

  9. Prochlorophytes • Characteristics • Chlorophylls A & B • No phycobilisomes • Thylakoids in stacks of 2 • DNA microfibrils peripheral • Habitat • 1) Obligate symbionts, live within sea squirts; 2) Planktonic filaments in freshwater lakes. • Example- Prochloron

  10. Stromatolites • Stromatolite- rock-like deposition of carbonates and trapped sediments; formed by cyanobacteria and diatoms. • Age- 3.5 BYA. • Growth-deposition-growth-deposition. • S-shaped in growth= 1 year. • Florida, Bahamas, Australia.

  11. Cyanobacteria Produce Cyanotoxins • Neurotoxins- alkaloids that target the nervous system. • Anatoxin and saxitoxin. • Symptoms- staggering, muscle twitching, gasping, and convulsions. • Anabaena, Aphanizomenon, Oscillatoria. • Hepatotoxins- large compounds that target the liver. • Microcystins and nodularins. • Symptoms- weakness, vomiting, diarrhea. • Anabaena, Microcystis, Oscillatoria, Nodularia, Nostoc.

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