The nitrogen-fixing bacteria found in the root nodules of leguminous plants are

Rhizobium lives symbiotically in the nodules of pulses and converts atmospheric nitrogen into ammonia, which the plant can use. Azotobacter is a free-living nitrogen fixer, Nitrosomonas converts ammonia to nitrite in nitrification, and Pseudomonas is involved in denitrification. Symbiotic is the key word, as it points to Rhizobium.