Nitrosopumilus

Nitrosopumilus maritimus is an extremely common archaeon living in seawater. It is the first member of the Group 1a Thaumarchaeota to be isolated in pure culture. Gene sequences suggest that the Group 1a Thaumarchaeota are ubiquitous with the oligotrophic surface ocean and can be found in most non-coastal marine waters around the planet. It is one of the smallest living organisms at 0.2 micrometers in diameter. It lives by oxidizing ammonia to nitrite. "N. maritimus" is capable of oxidizing ammonia at levels as low as 10 nanomolar, near the limit to sustain its life. "N. maritimus" lives in oxygen-depleted habitats. Oxygen needed for ammonia oxidation might be produced by novel pathway which generates oxygen and dinitrogen. "N. maritimus" is thus among organisms which are able to produce oxygen in dark.
This organism was isolated from sediment in a tropical tank at the Seattle Aquarium by a group led by David Stahl (University of Washington).
In taxonomy, ""Candidatus" Nitrosopumilus" is a genus of the Nitrosopumilaceae.
Taxonomy.
Cladogram was taken from Annotree v1.2.0. which uses the GTDB 05-RS95 (Genome Taxonomy Database).