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).