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FIU BOT4404 Lecture Notes

  • ️Frank J. Jochem
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Cyanobacteria Cyanobacteria Systematics
  • Classical approach: growth form and presence/abscence of morphological features: 5 groups (orders) 

    •     1. Unicelluar (rods or cocci) - Synechococcus
        2. Pleurocapsalean - unicells which produce endospores - Dermocarpa
        3. Non-heterocystous filaments - Spirulina, Oscillatoria, Trichodesmium. 
        4. Heterocystous unbranched filaments - Anabaena, Nostoc 
        5. Heterocystous branched filaments - Scytonema, Fisherella. 
  • Molecular Systematics: heterocystous and non-heterocystous forms in separate clusters; Prochlorophytes do not form cluster

Cyanobacteria Reproduction
  • Asexual reproduction 
  • Sexual reproduction: unknown
Cyanobacteria Evolution
  • Cyanobacteria are the oldest photosynthetic organisms. Oldest fossils from Australia date 3.5 billion years ago

  • Cyanobacteria changed our atmosphere into oxygen-rich air; they provided the basis for today‘s lifeforms but caused mass mortality in old, anaerobic bacteria forms
  • Fossil cyanobacteria appear very similar to today‘s forms and evolution seems to have been very slow in this group
  • Stromatolites date back as early as 2.7 billion years ago. Maximum 700-800 million years ago. Only 20 modern habitats

Cyanobacteria Photosynthesis
  • Pigments: Chl. a, b, carotenoids, phycobilins
  • Chl. b restricted to prochlorophytes
  • Phycobilins:
    • Phycocyanin, phycoerythrin, allophycocyanin, bound to proteins (phycobiliproteins)
    • Phycobilins close the „gap“ in the absorption spectra of chlorophyll and carotenoids and act as antenna pigments
    • Blue-green CB contain phycocyanin, redish CB contain phycoerythrin
    • Phycobiliproteins are located in disk-shaped or hemispherical phycobilisomes on the surface of thylakoids
    • Phycoerythrin exhibits yellow autofluorescence

       
  • Carotenoids: b-carotene, xanthophylls (e.g. zeaxanthin)
  • Chromatic adaptation: some CB can change their color and pigment composition in response to light quality
  • Storage products: cyanophycean starch (does not react with iodine), cyanophycin particles (amino acids), volatin (polyphosphate particles)


    • Cyanophycin particles in the cyanobacterium Oscillatoria (dark blue to violet); centroplasm light blue; staining by Loeffler's methylene blue, 1000x bright field
Cyanobacteria Nitrogen Fixation Cyanobacteria in Extreme Habitats