Azotobacter chroococcum

Azotobacter chroococcum is a bacterium discovered in 1901 by Martinus Beijerinck, noted for his discovery of an infectious agent smaller than a bacterium which is responsible for tobacco mosaic disease, as well as his role in founding the field of virology. It has the ability to fix atmospheric nitrogen, and was the first aerobic, free-living nitrogen fixer discovered.