Scalindua" are the most abundant anammox bacteria in marine environments, so they are vital to the Earth's nitrogen cycle.

[3] It consists of the oxidization of ammonium using nitrite as an electron acceptor (both are fixed nitrogen) and subsequent generation of nitrogen gas: “NH4+ + NO2− = N2 + 2H2O (ΔG° = -357 kj mol-1)”[4] This reaction uses nitrite (NO2−) as a terminal electron acceptor to produce nitric oxide (NO), which is then combined with ammonium (NH4+) to produce the intermediate hydrazine (N2H4) and water (H2O).

[5] The half reactions may be represented as: “NO2− + 2H+ + e− = NO + H2O (E° = +0.38V) NO + NH4+ + 2H+ + 3e− = N2H4 + H2O (E° = +0.06V) N2H4 = N2 + 4H+ + 4e− (E° = -0.75V)”[4] This metabolic pathway occurs anaerobically, something that was once considered impossible as ammonium was thought to be inert in the absence of oxygen.

[6] In fact, the presence of oxygen over 2 μM inhibits the anammox pathway, which is why members of the proposed genus Scalindua respire anaerobically.

[7] The existence of membrane-bound cellular organelles is very unusual in prokaryotes, and appears to be limited to the members of the phylum Planctomycetota.

[8][9] Ammonium and methane are known to be relatively difficult to activate with reactions catalyzed by enzymes that make use of high-potential oxygen radicals, which are unavailable to anaerobic life, leading to the assumption that both compounds were effectively inactive in low oxygen environments.

[6] It was not until 1999 that the existence of anaerobic ammonium oxidation was first discovered in a wastewater treatment plant in The Netherlands and given the name “anammox,” which would later prove to be a key player as part of the marine nitrogen cycle.

[12] During the past, many microorganisms such as anammox bacteria may have escaped discovery due to their relatively low growth rates requiring very efficient biomass retention absent from classical methods of cultivation.

[13] With the use of biofilms to improve the culturability of organisms that naturally occur in biofilms, combined with the use of biomass retention to study slowly growing microorganisms under substrate limitation, a technique using sequencing batch reactors (SBR) was developed for the long-term enrichment, cultivation, and quantitative analysis of a very slowly growing microbial community.

[13] Phylogenetic analysis of the first anammox bacteria discovered concluded that the organisms branched deeply in the phylum, Planctomycetota, which was previously considered to be of limited environmental importance.

[10] Nitrogen loses that could only be explained by the process of anammox continued to be discovered in freshwater waste-treatment facilities around the world including North America, Asia, and multiple regions throughout Europe.

[11] In certain regions, such as the Golfo Dulce in Costa Rica, up to %35 of atmospheric nitrogen production in the water column can be attributed to Ca.

[11] In other regions such as the Black Sea, the world's largest anoxic basin, characterized by a large gradient in ammonium concentrations (high levels in deep water tapering off to only trace amounts in the suboxic zone), the apparent ammonium sink in the suboxic zone was identified to be the result of anaerobic oxidation by bacteria belonging to Ca.

are the most abundant members of Anammox bacteria known to date, making it very important in the world's aquatic environments.

The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN)[22] and National Center for Biotechnology Information (NCBI)[23] "Ca.

is the only taxonomic group of ammonium-oxidizing bacteria found in the Black Sea, the Benguela Oxygen minimum zone off the coast of Namibia, and the estuary of the Randers Fjord, Denmark.

[28] Marine sediments located in deep-sea methane seeps contain anammox bacteria associated with Candidatus Scalindua spp.

Kuenenia (41% abundance), have been found in the non-rhizosphere area of the saltmarsh grass Spartina alterniflora while only Ca.

Scalindua wagneri" are often used in wastewater treatment plants to reduce the adverse effects of nitrification and denitrification on the local environment.

[31] The use of anammox bacteria in wastewater treatment plants has a drastically reduced cost compared to previous denitrification methods.