They are gram-negative bacteria with a number of unusual traits. Characteristics of Cyanobacteria 1. The cyanobacteria are the largest and most diverse group of photosynthetic bacteria, which was previously known as blue green algae. 2. Cyanobacteria are true prokaryotes. 3. They vary greatly in shape and appearance. 4. They range in diameter from about 1 to 10 micron. 5. They may be unicellular and exist as colonies of many shapes, or form filaments called trichomes. 6. They have normal Gram-negative type cell wall. 7. They often use gas vesicles to move in the water, and many filamentous species have gliding motility. 8. Their photosynthetic system closely resembles that of eukaryotes because they have chlorophyll a and photosystem 11. They carry out oxygenic photosynthesis i.e., they use water as an electron donor and generate oxygen during photosynthesis. 9. Cyanobacteria use pigments and electron transport chain components are located in thylakoid membranes linked with particles called phycoblisomes. They contain phycocynain pigment and CO2 in them is assimilated through the Calvin Cycle. 10. Reserve food material in cyanobacteria is glycogen. 11. In cyanobacteria hormogonia, akinetes and heterocysts are also produced.
