Blue-green “bacteria” are commonly known by what name in modern microbiology?

Introduction / Context:
“Blue-green algae” or “blue-green bacteria” refers to photosynthetic prokaryotes that play major ecological roles (oxygen production, nitrogen fixation). Modern terminology prefers “cyanobacteria.”

Given Data / Assumptions:

• We match the historical name to the correct modern name.
• We recognize these are prokaryotes, not true algae.

Concept / Approach:
Cyanobacteria are photosynthetic bacteria containing pigments like chlorophyll a and phycocyanin. Despite the “algae” nickname, they are prokaryotes (no nucleus). They thrive in diverse habitats from oceans to freshwater and extreme environments.

Step-by-Step Solution:

Verification / Alternative check:
Introductory biology texts universally equate blue-green algae with cyanobacteria.

Why Other Options Are Wrong:

• A: Not a recognized scientific group name.
• C: Protozoa are eukaryotic and typically non-photosynthetic.
• D: “None of the above” is incorrect because cyanobacteria is correct.

Common Pitfalls:
Confusing cyanobacteria with eukaryotic algae due to the traditional name “blue-green algae.”

Final Answer:
Cyanobacteria