The cyanobacteria have chlorophyll a similar to green plants. These organisms(a) are unicellular, colonial or filamentous, marine or terrestrial algae(b) are surrounded by gelatinous sheath(c) perform both carbon and nitrogen reduction

The cyanobacteria are unicellular, colonial or filamentous, freshwater/marine or terrestrial algae. The colonies are generally surrounded by gelatinous sheath. They often form blooms in polluted water bodies. Some of these organisms can fix atmospheric nitrogen in specialised cells called heterocysts. They also undergo oxygenic photosynthesis. Therefore, cyanobacteria are involved in both carbon as well as nitrogen reduction.