Comammox

Comammox (COMplete AMMonia OXidiser) is the name for an organism that can first convert ammonia into nitrite and then into nitrate by a process called nitrification.[1] These two processes are commonly carried out by separate groups of microorganisms.[2] However, complete conversion of ammonia into nitrate by a single microorganism was predicted in 2006.[1] Almost ten years later the presence of such organisms was discovered within the nitrospira and the nitrogen cycle had to be updated.[3][4] The genomes revealed the presence of genes necessary for ammonia oxidation (e.g. amoA gene and hao cluster). Nearly two years after the discovery of comammox organisms, Nitrospira inopinata was the first complete nitrifier to be isolated in pure culture.[5] Kinetic and physiological analysis of Nitrospira inopinata demonstrated that this complete nitrifier has a high affinity for ammonia, slow growth rate, low maximum rate of ammonia oxidation, and high yield.[5]