Cyanobacteria or Blue Green Algae

Blue-green algae, also known as cyanobacteria, contain pigments that give them their distinct colors. Phycocyanin, a blue pigment, and phycoerythrin, a red pigment, are found in these organisms. The combination of chlorophyll and these pigments produces the characteristic blue-green color in some species, while others appear red, purple, brown, or black due to the presence of red pigments. Examples of blue-green algae species include Spirulina, Anabaena, Rivularia, Oscillatoria, and Nostoc.

Nostoc, for instance, is a freshwater cyanobacterium commonly found in ponds, ditches, and other bodies of water, as well as wet soil. It forms colonies that float in water like balls and are surrounded by a mucilage sheath, which can be seen with the naked eye and can be several centimeters thick.

a

b

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                                Blue-green algae (a) Glocapsa (b) Anabaena (c) Oscillatoria

Reproduction, Anatomy, and Habitat

Reproduction of Nostoc

Nostoc reproduces through asexual methods such as hormogonia, akinetes, and spore formation.

Hormogonia are short, motile filaments that break off from the main filament and develop into new Nostoc colonies.

Akinetes are enlarged cells with thickened walls that serve as resting stages, capable of surviving harsh environmental conditions. They release short filaments of cells that develop into new Nostoc filaments.

Sexual reproduction is absent in Nostoc.

Nostoc a blue-green alga 

Anatomy of Nostoc

Nostoc is a prokaryotic organism, lacking a true organized nucleus and membrane-bound organelles.

The genetic material in Nostoc consists of a circular strand of DNA, and ribosomes are abundant in the cytoplasm for protein synthesis.

Nostoc carries out photosynthesis in a specialized system of membranes located in the outer zone of the cytoplasm.

Nostoc uses chlorophyll "a" and photosystem II in its photosynthetic process, and phycobilins as accessory pigments, particularly phycocyanin, which gives it a blue-green color.

Carbon dioxide (CO₂) is assimilated through the Calvin cycle during photosynthesis.

 

Habitat of Nostoc

Nostoc is commonly found in freshwater habitats such as ponds, ditches, pools of water, and wet soil.

It forms jelly-like masses consisting of slender, long, and short filaments that are interwoven.

Transparent heterocysts, which are round or barrel-shaped cells, may be present in the trichome of Nostoc, and they can be terminal or intercalary.

Nostoc can exhibit different forms of life, including unicellular and solitary forms, colony forms, and filamentous forms attached end to end.

Nostoc may live in symbiosis or as epiphytes, depending on environmental conditions.

In conclusion, Nostoc is a species of blue-green algae that reproduces through asexual methods, lacks sexual reproduction, and carries out photosynthesis using chlorophyll "a," photosystem II, and phycobilins. It is commonly found in freshwater habitats and exhibits various forms of life.