the plant through Genetic engineering. • Thermus aquaticus is a thermophilic gram negative bacteria which produces Taq Polymerase a key enzyme for Polymerase Chain Reaction (PCR). • Methanobacterium is employed in biogas production. Halobacterium , an extremophilic bacterium grows in high salinity.
It is exploited for the production β carotene. Cyanobacteria are popularly called as 'Blue green algae' or 'Cyanophyceae'. They are photosynthetic, prokaryotic organisms. According to evolutionary record Cyanobacteria are primitive forms and are found in different habitats.
Most of them are fresh water and few are marine ( Trichodesmium and Dermacarpa ) Trichodesmium erythraeum a cyanobacterium imparts red colour to Red sea. Species of Nostoc , Anabaena lead an endophytic life in the coralloid root of Cycas , leaves of aquatic fern Azolla by establishing a symbiotic association and fix atmospheric nitrogen. Members like Gloeocapsa, Nostoc , Scytonema are found as phycobionts in lichen thalli. Salient features • 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 ( Oscillatoria ). • The protoplasm is differentiated into central region called centroplasm and peripheral region bearing chromatophore called chromoplasm. • The photosynthetic pigments include c-phyocyanin 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 , 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, Anabaena ).