Identify the correct example of cyanobacteria.
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Oscillatoria
Cyanobacteria (blue-green algae) are autotrophic microbes that live in water and on land. Many of them fix atmospheric nitrogen. In paddy fields they act as an important biofertiliser and also add organic matter to the soil.
(1) Glomus — Incorrect. Glomus is a fungus. It forms mycorrhiza with plant roots and passes phosphorus from the soil to the plant.
(2) Oscillatoria — Correct. Oscillatoria, like Anabaena and Nostoc, is a nitrogen-fixing cyanobacterium.
(3) Azospirillum — Incorrect. It is a bacterium that fixes nitrogen while living free in the soil. It is not a cyanobacterium.
(4) Azotobacter — Incorrect. It is also a free-living nitrogen-fixing soil bacterium.
NCERT Extract:
Microbes as Biofertilisers – …
