Russell, Virginia V.

Abstract Ni.tro.so.cal'dus. N.L. adj. nitrosus nitrous; L. masc. adj. caldus hot; N.L. masc. n. Nitrosocaldus a nitrite producer at thermophilic growth temperatures. Thermophilic, neutrophilic, autotrophic, and aerobic ammonia‐oxidizing archaea. Urea can be used as a source of energy for growth. Cells fix CO 2 via a modified 3‐hydroxypropionate/4‐hydroxybutyrate carbon fixation pathway. Cells are irregular cocci between 0.65 and 0.75 microns in diameter. Cells reproduce by binary fission. Cell membrane lipids consist mainly of acyclic and cyclized glycerol trialkyl glycerol tetraethers (GTGTs) and glycerol dibiphytanyl glycerol tetraethers (GDGTs), with acyclic GTGT and crenarchaeol as the dominant components. Quinone systems include menaquinones with fully saturated and monounsaturated side chains that comprised six isoprenoid units. The members of the genus Ca . Nitrosocaldus can be found in neutral or slightly alkaline terrestrial geothermal environments at temperatures ranging from 65 to 85°C. Phylogenetic analysis on the basis of both 16S rRNA and amoA genes supports the monophyletic genus Ca . Nitrosocaldus within the family Ca . Nitrosocaldaceae. DNA G + C content (mol%) : 37.1. Type species : Ca . Nitrosocaldus yellowstonensis (Nitrosocaldus yellowstonii) de la Torre, Walker, Ingalls, Könneke and Stahl 2008, 815. Taxonomic and Nomenclature Notes According to the List of Prokaryotic names with Standing in Nomenclature (LPSN), the taxonomic status of the genus Candidatus Nitrosocaldus is: preferred name (not correct name) (last update, February 2025) * . LPSN classification: Archaea / Thermoproteati / Thermoproteota / incertae sedis / Candidatus Nitrosocaldales / Candidatus Nitrosocaldaceae / Candidatus Nitrosocaldus The genus Candidatus Nitrosocaldus can also be recovered in the Genome Taxonomy Database (GTDB) as g__Nitrosocaldus (version v220) ** . GTDB classification: d__Archaea / p__Thermoproteota / c__Nitrososphaeria / o__Nitrososphaerales / f__Nitrosocaldaceae / g__Nitrosocaldus * Meier‐Kolthoff et al. ( 2022 ). Nucleic Acids Res , 50 , D801 – D807 ; DOI: 10.1093/nar/gkab902 ** Parks et al. ( 2022 ). Nucleic Acids Res , 50 , D785 – D794 ; DOI: 10.1093/nar/gkab776

Abstract Ni.tro.so.cal.da'les. N.L. masc. n. Nitrosocaldus type genus of the order; ‐ ales ending to denote order; N.L. fem. pl. n. Nitrosocaldales the Nitrosocaldus order. Coccoid cells reproduce by binary fission. Thermophilic and neutrophilic. Obligately aerobic. Chemolithoautotrophic growth by ammonia oxidation to nitrite using CO 2 as carbon source. Some members can also use urea as an alternative source of energy for growth. Cell membrane is composed of isoprenoid tetraether lipids, including large amounts of acyclic and cyclized glycerol trialkyl glycerol tetraethers (GTGTs) and crenarchaeol (a unique glycerol dibiphytanyl glycerol tetraether (GDGT) containing one cyclohexane ring and four cyclopentane rings). Fully saturated and monounsaturated menaquinones with six isoprenoid units are present. They are globally distributed in various geothermal environments. Phylogenetic analyses of 16S rRNA and amoA gene sequences place the monophyletic order Ca . Nitrosocaldales as a basal lineage within the phylum Thaumarchaeota . This order can be distinguished from the closest order Nitrososphaerales by a lower mol% G + C content, a higher growth temperature (>60°C), and a higher relative abundance of GTGT. The order Ca . Nitrosocaldales is currently represented by a single family Ca . Nitrosocaldaceae. Type genus : Ca . Nitrosocaldus de la Torre, Walker, Ingalls, Könneke and Stahl 2008, 815. Taxonomic and Nomenclature Notes According to the List of Prokaryotic names with Standing in Nomenclature (LPSN), the taxonomic status of the order Candidatus Nitrosocaldales is: preferred name (not correct name) (last update, February 2025) * . LPSN classification: Archaea / Thermoproteati / Thermoproteota / incertae sedis / Candidatus Nitrosocaldales The order Candidatus Nitrosocaldales can also be recovered in the Genome Taxonomy Database (GTDB) as o__Nitrososphaerales (version v220) ** . GTDB classification: d__Archaea / p__Thermoproteota / c__Nitrososphaeria / o__Nitrososphaerales * Meier‐Kolthoff et al. ( 2022 ). Nucleic Acids Res , 50 , D801 – D807 ; DOI: 10.1093/nar/gkab902 ** Parks et al. ( 2022 ). Nucleic Acids Res , 50 , D785 – D794 ; DOI: 10.1093/nar/gkab776

Abstract Ni.tro.so.cal.da.ce'ae. N.L. masc. n. Nitrosocaldus type genus of the family; ‐ aceae ending to denote family; N.L. fem. pl. n. Nitrosocaldaceae the Nitrosocaldus family. Cells are irregular cocci and divide by binary fission. Strictly aerobic. Thermophilic, neutrophilic, and lithoautotrophic archaea that are able to gain energy via ammonia oxidation to nitrite. Membrane lipids contain glycerol dibiphytanyl glycerol tetraethers (GDGTs) bound to monoglycosidic, diglycosidic, phosphohexose, and hexose‐phosphohexose headgroups. Like other described Thaumarchaeota , members of this family contain crenarchaeol as a major membrane core lipid. However, their membrane lipids are characterized by the presence of the high abundances of acyclic and cyclized glycerol trialkyl glycerol tetraethers (GTGTs). Respiratory lipoquinones are saturated and monounsaturated menaquinones with six isoprenoid units. Cells and molecular markers have been found in neutral or slightly alkaline geothermal environments, such as hot springs and subsurface gold mines. At present, the family Ca . Nitrosocaldaceae only harbors a single genus, which is so far represented by only one species. Therefore, future phylogenetic analysis of additional cultivated representatives may reveal further subdivisions within the family. DNA G+C content (mol%):36.8–41.7%. Type genus: Candidatus Nitrosocaldus de la Torre, Walker, Ingalls, Könneke and Stahl 2008, 815. Taxonomic and Nomenclature Notes According to the List of Prokaryotic names with Standing in Nomenclature (LPSN), the taxonomic status of the family Candidatus Nitrosocaldaceae is: preferred name (not correct name) (last update, February 2025) * . LPSN classification: Archaea / Thermoproteati / Thermoproteota / incertae sedis / Candidatus Nitrosocaldales / Candidatus Nitrosocaldaceae The family Candidatus Nitrosocaldaceae can also be recovered in the Genome Taxonomy Database (GTDB) as f__Nitrosocaldaceae (version v220) ** . GTDB classification: d__Archaea / p__Thermoproteota / c__Nitrososphaeria / o__Nitrososphaerales / f__Nitrosocaldaceae * Meier‐Kolthoff et al. ( 2022 ). Nucleic Acids Res , 50 , D801 – D807 ; DOI: 10.1093/nar/gkab902 ** Parks et al. ( 2022 ). Nucleic Acids Res , 50 , D785 – D794 ; DOI: 10.1093/nar/gkab776