Microbes in Human Welfare — BIOLOGY STD 12 Science — Question

Cyanobacteria- e.g. Nostoc and Anabaena act as source of biofertilizers. Cyanobacteria possess heterocysts that fix atmospheric nitrogen.
A. azolae, makes symbiotic relationship with aquatic fern Azolla, acts as a good biofertilizer for rice fields. Fixed nitrogen mixes with soil, from where it is absorbed by plant roots. In this way cyanobacteria are main source of biofertilizer.