Biofertilizers are organisms that enrich the nutrient quality of the soil. The main sources include bacteria like Rhizobium (which fixes atmospheric nitrogen symbiotically), cyanobacteria like Nostoc (which fixes atmospheric nitrogen), and fungi forming Mycorrhiza (which absorb phosphorus). Agrobacterium is typically known as a pathogen or a vector used in biotechnology for gene transfer, not as a biofertilizer , , .