Cyanobacteria
Cyanobacteria are prokaryotes that encompass a wide range of photosynthesing bacteria, which as the name suggests belong to the domain of bacteria[1].
Cyanobacteria are regarded as critical in the formation of the atmosphere that we have today, even though they were not the first organisms capable of photosynthesis. Some have a vital role within ecology, for example Heterocysts which produce enzymes capable of fixing Nitrogen. Other species can be endosymbiotic and some are known to produce toxins know as cyanotoxins[2].