Question

List out the salient features of cyanobacteria?

Answer 1

• The members of this group are prokaryotes and lack motile reproductive structures.
• The thallus is unicellular in Chroococcus, colonial in Gloeocapsa and filamentous trichome in Nostoc.
• Gliding movement is noticed in some species (Oscillatorid).
• The protoplasm is differentiated into central region called centroplasm and peripheral region bearing chromatophore called chromoplasm.
• The photosynthetic pigments include c – phydcyanin and c – phycoerythrin along with myxoxanthin and myxoxanthophyll.
• The reserve food material is cyanophycean starch.
• In some forms a large colourless cell is found in the terminal or intercalary position called heterocysts. They are involved in nitrogen fixation
• They reproduce only through vegetative methods and produce akinetes (thick wall dormant cell formed from vegetative cell), hormogonia (a portion of filament get detached and reproduce by cell division), fission and endospores.
• The presence of mucilage around the thallus is characteristic feature of this group. Therefore, this group is also called Myxophyceae.
• Sexual reproduction is absent.
• Microcystis aeruginosa and Anabaena flos – aquae cause water blooms and release toxins and affect the aquatic organism. Most of them fix atmospheric nitrogen and are used as biofertilizers (Example: Nostoc and Anabaena). Spirulina is rich in protein hence it is used as single cell protein.