Cyanobacteria Cy·a·no·bac·te·ri·a (sī'ə-nō-bāk-tēr'ē-ə)
n.
A group of Procaryotae consisting of unicellular or filamentous gram-negative microorganisms that are either nonmotile or possess a gliding motility, may reproduce by binary fission, and photosynthetically produce oxygen; some species capable of fixing nitrogen. Members of this phylum were formerly called blue-green algae.