Key Processes and Prokaryotes in the Nitrogen Cycle Processes Example organisms Nitrification (NH+-NO3) NH4→NO2 Nitrosomonas NO2→NO3 Nitrobacter Denitrification (NO3-N2) Bacillus,Paracoccus, Pseudomonas N2 Fixation (N2+8 H-NHg+H2) Free-living Aerobic Azotobacter Cyanobacteria Anaerobic Clostridium,purple and green phototrophic bacteria Methanobacterium (Archaea) Symbiotic Rhizobium Bradyrhizobium Frankia Ammonification (organic-N-NH4+) Many organisms can do this Anammox (NO2+NH3-2 N2) Brocadia 2012 Pearson Education,Inc