I am really confused. On google and other places(though very old) it is mentioned that Cynobacteria are the same as BGA(Blue-Green Algae) and are technically bacteria and are places under the kingdom monera. However, in some places is it mentioned that they are not the same and so does my teacher. It is mentioned that Cynobacteria, being a unicellular prokaryote is placed under Monera.

So, I have 3 Questions -

  1. Are Cynobacteria and BGA the same?
  2. Is Cynobacteria a monera or protista ? is it a prokaryote or euakryote ?
  3. Is BGA a monera or protista ? is it a prokaryote or eukaryote ?

Is it true that later it was believed that Cynobacteria and BGA were the same, and now it has been discovered that they are different?

What is the true fact?

I believe this community has experienced biologists, hence I have reached out here.

Please understand that I am a student and this question might sound amateur, so please ignore that and please help clear my confusion.

Any help would be appreciated !


1 Answer 1


Cyanobacteria are oxygenic photosynthic prokariotes, historically known as "blue-green algae" until their prokariotic nature was unambiguously confirmed. (So, yes, Cyanobacteria and blue-green algae are the same, but they are not algae.)

Since their prokaryotic nature has unambiguously been proven, the term “cyanobacteria” (or occasionally “cyanoprokaryotes”) has been adopted in the scientific literature. ... the taxon Oxyphotobacteria is proposed for cyanobacteria in a strict sense.

Taxonomy has been a big problem for this/these organism(s); there are entire papers arguing the case for various taxonomic classifications.

It cannot be in the kingdom Protista as it is not a eukaryote. (So, they are in the kingdom Monera.)

Is BGA a monera or protista ? is it a prokaryote or eukaryote ?

Blue-green algae is a historical term and incorrectly describes what is now called Cyanobacteria. The question is not answerable as written, but if it has to have an answer, I'd go with "monera" and "prokaryote".

Chorus, I, Welker M; eds. 2021. Toxic Cyanobacteria in Water, 2nd edition. CRC Press, Boca Raton(FL), on behalf of the World Health Organization, Geneva, CH.


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