cyanobacteria

Cyanobacteria , also known as Cyanophyta, is a phylum of bacteria that obtain their energy through photosynthesis. The name “cyanobacteria” comes from the color of the bacteria ( = blue). They are often called blue-green algae, but some consider that name a misnomer, as cyanobacteria are prokaryotic and algae should be eukaryotic, although other definitions of algae encompass prokaryotic organisms. By producing gaseous oxygen as a byproduct of photosynthesis, cyanobacteria are thought to have converted the early reducing atmosphere into an oxidizing one, which dramatically changed the composition of life forms on Earth by stimulating biodiversity and leading to the near-extinction of oxygen-intolerant organisms. According to endosymbiotic theory, the chloroplasts found in plants and eukaryotic algae evolved from cyanobacterial ancestors via endosymbiosis.