The prokaryotic organisms which carry out the process of photosynthesis by using sunlight and oxygen are known as cyanobacteria. In almost every environmental condition these bacterias are present which includes freshwater, soil, lichen, and seawater. In order to reduce carbon dioxide during reactions, these bacterias use water as the source of electrons. Cyanobacteria are considered to be photoautotrophs for these reasons.To learn more about cyanobacteria, students can visit Vedantu.