Free Living Bacteria

Cyanobacteria (or blue-green algae) Anabaena and Nostoc and genera such as Azotobacter, Bacillus, Beijerinckia, Clostridium, Desulfovibrio and Klebsiella.

Mutualistic Bacteria

Rhizobium, associated with leguminous plants, and various Azospirillum species, associated with cereal grasses.