Bacteria such as Azotobacter, Pseudomonas, Clostridium etc. capture nitrogen from air and mix it with soil. Rhizobium fixes nitrogen from the air in the roots of leguminous plants. Rhizobium is currently being used as a microbial fertilizer. Three species of Rhizobium form nodules on lentil roots. These are Rhizobium bangladashense, Rhizobium bine and Rhizobium lentis. Bangladeshi scientist Dr. Harun or Rashid discovered these three species.