Class 12 NEET Biology Microbes in Human Welfare

(d) : Biofertilizers are organisms which bring about nutrient enrichment of the soil. Azotobacter is a free living, aerobic, nitrogen fixing bacteria. Anabena is a nitrogen fixing cyanobacteria that occurs in both free living and symbiotc associations with Azolla, Cycas roots, etc. Rhizobium lives symbiotically in root nodules of legumes and nonlegumes. Vesicular-arbuscular mycorrhiza (VAM) is an example of endomycorrhiza in which fungal hyphae penetrate the cortical cells of grasses to form vesicles.