cyanobacterium

/S AY0 AE1 N AH0 B AE0 K T IH1 R IY0 AH0 M/
noun
  1. 1

    Any of very many photosynthetic prokaryotic microorganisms, of phylum Cyanobacteria, once known as blue-green algae.

Source: https://en.wiktionary.org/wiki/cyanobacterium