biostudies-literatureUnknown84(19)Sauder LAGouvernement du Canada | Natural Sciences and Engineering Research Council of CanadaAmmonia is a metabolic waste product excreted by aquatic organisms that causes toxicity when it accumulates. Aquaria and aquaculture systems therefore use biological filters that promote the growth of nitrifiers to convert ammonia to nitrate. Ammonia-oxidizing bacteria (AOB) have been isolated from aquarium biofilters and are available as commercial supplements, but recent evidence suggests that ammonia-oxidizing archaea (AOA) are abundant in aquarium biofilters. In this study, we report the cultivation and closed genome sequence of the novel AOA representative "<i>Candidatus</i> Nitrosotenuis aquarius," which was enriched from a freshwater aquarium biofilter. "<i>Ca</i> Nitrosotenuis aquarius" oxidizes ammonia stoichiometrically to nitrite with a concomitant increase in thaumarchaeotal ceApplied and environmental microbiologye01430-18https://www.ebi.ac.uk/biostudies/studies/S-EPMC6146995biostudies-literature"Candidatus Nitrosotenuis aquarius," an Ammonia-Oxidizing Archaeon from a Freshwater Aquarium Biofilter.PMC6146995Chain PSauder LANeufeld JDLo CCEngel Kfalse"Candidatus Nitrosotenuis aquarius," an Ammonia-Oxidizing Archaeon from a Freshwater Aquarium Biofilter.Ammonia is a metabolic waste product excreted by aquatic organisms that causes toxicity when it accumulates. Aquaria and aquaculture systems therefore use biological filters that promote the growth of nitrifiers to convert ammonia to nitrate. Ammonia-oxidizing bacteria (AOB) have been isolated from aquarium biofilters and are available as commercial supplements, but recent evidence suggests that ammonia-oxidizing archaea (AOA) are abundant in aquarium biofilters. In this study, we report the cultivation and closed genome sequence of the novel AOA representative "<i>Candidatus</i> Nitrosotenuis aquarius," which was enriched from a freshwater aquarium biofilter. "<i>Ca</i> Nitrosotenuis aquarius" oxidizes ammonia stoichiometrically to nitrite with a concomitant increase in thaumarchaeotal ce2018-01-01T00:00:00Z2018 Oct2026-05-01T17:48:16.472Z2026-04-07T17:10:04.633ZS-EPMC61469952995925610.1128/aem.01430-1810.1128/AEM.01430-18