Which of the following is not a cyanobacteria ?

The correct answer is Option (2) → Glomus

Option (1) Nostoc — A cyanobacterium. It fixes nitrogen in paddy fields.

Option (2) Glomus — Not a cyanobacterium. Glomus is a fungus that forms mycorrhiza with plant roots and helps them absorb phosphorus.

Option (3) Anabaena — A cyanobacterium. It fixes atmospheric nitrogen.

Option (4) Oscillatoria — A cyanobacterium. NCERT names it with Anabaena and Nostoc.

Note: A similar question was also asked in CUET (UG) 2026 on 26-05-2026 (Slot 1).

NCERT Extract:
Microbes as Biofertilisers – “… Fungi are also known to form symbiotic associations with plants (mycorrhiza). Many members of the genus Glomus form mycorrhiza. The fungal symbiont in these associations absorbs phosphorus from soil and passes it to the plant. Plants having such associations show other benefits also, such as resistance to root-borne pathogens, tolerance to salinity and drought, and an overall increase in plant growth and development.”
Microbes as Biofertilisers – “Cyanobacteria are autotrophic microbes widely distributed in aquatic and terrestrial environments many of which can fix atmospheric nitrogen, e.g. Anabaena, Nostoc, Oscillatoria, etc.”