Cyanobacteria all live in aquatic environments and use photosynthesis to make their own food. Additionally, all cyanobacteria belong to the larger class of bacteria, which is one of the largest groups of organisms. Most cyanobacteria are unicellular, and they typically live in large colonies.
Cyanobacteria are among the oldest organisms on Earth. They arose during the Proterozoic era, emerging with the generation of nutrient-rich oil deposits that appeared during that period. According to Berkeley College, cyanobacteria are often called “blue-green algae” because of their residence in aquatic settings and ability to perform photosynthesis. These bacteria, however, are not related to other algae, which belong in the kingdom Plantae.