The following points highlight the two common examples of Cyanobacteria. The examples are: 1. Spirulina and 2. Nostoc.
It is a spirally coiled free floating filamentous blue green alga or cyanobacterium of up to 0.5 mm length. The trachoma’s appear to be unicellular but staining and electron microscopy has shown the presence of thin transverse walls. The ends are rounded. It is also being cultured. It can grow both autotrophically and heterotrophically. Trachoma’s show rotary and bending movements.
This cyanobacterium is rich in protein (55% to 68%). It also contains minerals, vitamins (including B12) and essential fatty acids. Because of its beneficial nature, Spirulina is used as food additive in the form of powder, pill or tablet. WHO has called it as greatest super food. It is being produced on mass scale by NBR1 Lucknow and CFTRI Mysore.
Spirulina is also a good food supplement for animal feed. However, it should not form more than 10% of their diet. The cyanobacterium is also used as manure. It is helpful in reclamation of usar soils. It has antiviral and anticancer properties, strengthening immune system of the body.
It is a colonial cyanobacterium that is popularly called moon spit, fallen star or star jelly. Nostoc occurs in both aquatic and sub aerial habitats. It also forms symbiotic association with Anthoceros, Cycad roots, Gunnera stems and Trifolium roots. A colony contains a number of flexuous intertwined filaments on the periphery, a mucilage filled hollow interior and a dense mucilage covering on the outside.
Each trichome is beaded. S-shaped and consists of a large number of vegetative cells, a few terminal and intercalary large pale coloured heterocyst’s and thick-walled resting cells called akinetes. Heterocyst’s are specialised to perform nitrogen fixation.
Reproduction occurs through fragmentation, hormogones, akinetes and occasionally by heterocysts. Larger colonies of Nostoc are eaten in China and nearby areas. Because of its ability of nitrogen fixation, Nostoc enriches its habitat with nitrogen. It is also used in reclaiming barren land and usar soil.