Microalgae

• Protist


  Any eukaryotic organisms that is not animal, plant, fungus
• Protist


  • Have chlorophyll and accessory pigments for photosynthesis
  • Variations in cell structure—unicellular, colonial and multicellular forms

  
• Algal forms


  • Unicells (solitary)
  • Multicellular (filaments, chain)
  • Aggregations (strictly colonial)
• Reproduction


  • Vegetative (Hormogonia)
  • Asexual (spores)
  • Sexual & Binary fission
  • Sexual & Asexual
• Resting Cysts


  Unfavorable condition<|>Withstand extreme condition<|>Settle at the seafloor; afloat<|>Can last for long time
• Resting Cysts of diatoms

  Siliceous resting cyst = statosphora, stomacyst, statocyst
• Prokaryotic Algae


  No nuclear region and complex organelles—chloroplasts, mitochondria, Golgi bodies, and endoplasmic reticula<|>Cyanobacteria. Chlorophylls are on internal membranes of flattened vesicles called thylakoids-contain photosynthetic pigments

  
• Eukaryotes


  Distinct chloroplast, nuclear region and complex organelles<|>Thylakoids are grouped into grana<|>Pyrenoids are centers of carbon dioxide fixation within the chloroplasts of algae
• Five (5) Main Taxonomic Groups

  • Bacillariophyta
  • Xanthophyceae
  • Chrysophyceae
  • Dinoflagellates
  • Cyanobacteria
  • Euglenoids
  • Chlamydomonas
• Bacillariophyta (Diatoms)


  • Siliceious cell walls = frustules
  • Nonmotile / sliding movements
  • Chlorophyll : a & c
  • Pigments : beta-carotene, phycoxanthin, xanthophyll
  • Storage: Leucosin, lipid, volutin
  • Pennate, centric

  
• Diatom Frustules


  Epitheca: Larger = older valve of the frustule with the girdle elements (epicingulum) connected with it<|>Hypotheca: Smaller = younger valve of the frustule with the girdle elements (hypocingulum) connected with it<|>Connective Zone: This zone is composed of the overlapping girdle elements of the diatom (the epicingulum and hypocingulum)<|>Septa: Partitions that are formed within the valves. It can be used to characterize diatoms<|>Raphe: occurs in pennate diatoms as an elongated fissure in a valve. The raphe is used by diatom for movement. It is important for identification
• ~50 harmful species of Dinoflagellates
• ~100 harmful species of Diatoms
• ~10 harmful species of Cyanobacteria
• Xanthophyceae (Yellow-green algae)


  • live primarily in freshwater, though some are found in marine waters, in damp soil, or on tree trunks
  • Pigments: xanthophylls and beta carotene
  • single-celled flagellates to simple colonial and filamentous forms
  • cell wall is unknown but inside some there are two silica valves similar to those in diatoms
  • For the species that are filamentous the interlocking halves are in the shape of a H

  
• Chrysophyceae (Golden-brown algae)


  • Found mostly in freshwater
  • often unicellular and have a flagellum, allowing them to be mobile in the water
  • presence of a siliceous cyst : statospore, stomatocyst, statocyst
  • this structure usually contains a single pore
  • The surface of mature cysts are useful to distinguish species

  
• Major Orders


  • Gymnodiniales
  • Peridiniales
  • Dinophysiales
  • Prorocentrales
  • Gonyaulacales
  • Peridiniales
• Peridiniales


  • Biflagellated and free-swimming
  • A few are non-motile unicells reproducing by motile specialized cells (zoospores and gametes)
• Gymnodiniales


  "naked" - Members are known as gymnodinioid Athecate (lacking on armored exterior)
• Gymnodiniales


  • Karenia brevis
  • Gyrodinium spiralae
  • Karlodinium veneficum
• Orders


  • Prorocentrales
  • Dinophysiales
  • Dinamoebales
• PHYLUM: Chlorophyta (green algae)
• Chlorophyta


  • Habitat: Marine, freshwater (90%) (CHAROPHYTA), symbiotic
  • Both unicellular and multicellular
  • Photosynthetic pigments: Chlorophyll a and b, xanthophylls, carotenes
  • Food reserves: Grainy starch
  • Produces black color in response to iodine (IKI +)
  • Cell wall : Polysaccharides, sometimes cellulose
  • Reproduction : Asexual and sexual
  • The chloroplast may be discoid, plate-like, reticulate, cup-shaped, spiral or ribbon shaped in different species
• Asexual reproduction


  1. Growth Phase - During this phase the cells grow in size by utilizing the photosynthetic products

  2. Ripening phase - In this phase the cells mature and prepare themselves for division

  3. Post ripening phase - During this phase, each mature cell divides twice either in dark or in light. The cells formed in dark are known as dark to light phase, cells again grow in size

  4. Division Phase - During this phase the parent cell wall ruptures and unicells are released
• Cyanophyta are Gram-negative bacteria that obtain energy via photosynthesis
• Cyanobacteria appear to have originated in freshwater or a terrestrial environment
• Phototrophic eukaryotes such as green plants perform photosynthesis in plastids that are thought to have their ancestry in cyanobacteria, acquired long ago via a process called endosymbiosis
• These endosymbiotic cyanobacteria in eukaryotes then evolved and differentiated into specialized organelles such as chloroplasts
• Cyanobacteria produce a range of toxins known as cyanotoxins that can pose a danger to humans and animals
• Cyanobacteria


  • Some filamentous species can differentiate into several different cell types: Vegetative cells, Akinetes, Heterocysts
• Heterocysts contain the enzyme nitrogenase, vital for nitrogen fixation
• Heterocyst-forming species are specialized for nitrogen fixation and are able to fix nitrogen gas into ammonia, nitrites, or nitrates, which can be absorbed by plants and converted to protein and nucleic acids
• Biotechnology potential


  Synechocystis and Cyanothece are important model organisms with potential applications in biotechnology for bioethanol production, food colorings, as a source of human and animal food, dietary supplements and raw materials
• Cyanobacterial growth is favored in ponds and lakes where waters are calm and have little turbulent mixing
• The growth of opportunistic species can lead to harmful blooms and toxin production with negative consequences to human health, livestock and fish stocks
• Growth is also favored at higher temperatures which enable Microcystis species to outcompete diatoms and green algae, and potentially allow development of toxins
• Cyanobacteria can interfere with water treatment in various ways: by producing cyanotoxins, which have the potential to cause serious illness if consumed
• Euglenophyta (flagellates) are commonly found in freshwater, especially when it is rich in organic materials, with a few marine and endosymbiotic members
• Many euglenids feed by phagocytosis, or strictly by diffusion
• Euglenales (983 species) have chloroplasts and produce their own food through photosynthesis