Nitrososphaeria
| Nitrososphaeria | |
|---|---|
| Nitrosopumilus maritimus , partially with virions of Nitrosopumilus spindle-shaped virus 1 (Thaspiviridae ) attached. | |
| Scientific classification Edit this classification | |
| Domain: | Archaea |
| Kingdom: | Thermoproteati |
| Phylum: | Thermoproteota |
| Class: | Nitrososphaeria Stieglmeier et al. 2014[1] |
| Orders[1] | |
| Synonyms | |
| |
Nitrososphaeria (previously phylum Nitrososphaerota or Thaumarchaeota[3] ) is a class of Archaea under the phylum Thermoproteota.[4] The first species, Cenarchaeum symbiosum, was discovered in 1996 and was found to have a genome distinct from other known archaea at the time; hence, it was classified as a separate phylum. A decade later, three ammonia-oxidizing archaea were described, Nitrosopumilus maritimus , Nitrososphaera viennensis , and Nitrososphaera gargensis . Genome analysis in 2010 revealed that C. symbiosum and the three archaea are genetically of the same group.
Taxonomic reassessment in 2021 merged the archaeal group to the phylum Thermoproteota. Most species of Nitrososphaeria are chemolithoautotrophic ammonia-oxidizers and may play important roles in biogeochemical cycles, such as the nitrogen cycle and the carbon cycle. Metagenomic sequencing indicates that they constitute ~1% of the sea surface metagenome across many sites.[5] The lipid crenarchaeol has been found only in Nitrososphaeria, making it a potential biomarker for the class.[6] [7]
Nitrososphaeria-derived membrane-spanning tetraether lipids (glycerol dialkyl glycerol tetraethers; GDGTs) from marine sediments can be used to reconstruct past temperatures via the TEX86 paleotemperature proxy, as these lipids vary in structure according to temperature.[8] Because most Nitrososphaeria seem to be autotrophs that fix CO2, their GDGTs can act as a record for past Carbon-13 ratios in the dissolved inorganic carbon pool, and thus have the potential to be used for reconstructions of the carbon cycle in the past.[6]
Taxonomy
[edit ]In 1996, biologists at the University of California discovered archaea present in a sponge (Axinella sp.) which they had collected from the offshore of Santa Barbara. Genetic analysis showed that the archaea was different but related to Crenarchaeota, the major group of archaea known at the time. As a distinct species, it was named Cenarchaeum symbiosum.[9] [10] Further studies based on ribosomal RNA genes and DNA polymerase began to indicate that the archaea was not closely related to Crenarchaeota.[11] [12]
In 2005, a team of German and American biologists at the University of Washington discovered ammonia-oxidizing archaea from various water sources around Seattle and gave the name Nitrosopumilus maritimus.[13] It was classified under the phylum Crenarchaeota. Another related ammonia-oxidizing archaea, Nitrososphaera gargensis, was discovered in 2008 from Siberian Garga hot spring.[14] By then, C. symbiosum was established as capable of oxidizing ammonia.[15] Genome sequence showed that the group differ significantly from other members of the hyperthermophilic Crenarchaeota .[16] [2] [17] Two phyla of archaea were recognized: Crenarchaeota and Euryarchaeota. Since the genetic difference of the ammonia-oxidizing archaea was huge from member of the two existing phyla, a third phylum Thaumarchaeota was introduced in 2008.[2] The classification was based on phylogenetic data, such as the sequences of these organisms' ribosomal RNA genes, and the presence of a form of type I topoisomerase that was previously thought to be unique to the eukaryotes.[18]
In 2014, Nitrososphaera viennensis was discovered from a garden soil in Vienna, Austria, for which Michaela Stieglmeier and her colleagues created the taxonomic hierarchy, family Nitrososphaeraceae, order Nitrososphaerales and class Nitrososphaeria.[19] International Code of Nomenclature of Prokaryotes (ICNP, Prokaryotic Code), Aharon Oren and George M. Garrity fomralized in 2021 the phylum as Nitrososphaerota for the ammonia-oxidizing archaea, since Stieglmeier's classification was the first valid publication.[20] At the same time, a team of Australian scientists led by Christian Rinke and Philip Hugenholtz published a new classification on archaea, in which they merged Crenarchaeota and Nitrososphaerota (in fact the entire TACK superphylum) into the phylum Thermoproteota, thereby demoting the phylum to the class level.[21]
Classification and diversity
[edit ]The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN)[25] and National Center for Biotechnology Information (NCBI)[26]
"Ca. Geothermarchaeum"
"Ca. Scotarchaeum"
"Ca. Australarchaeum"
"Ca. Gagatemarchaeum"
"Ca. Nitrosothermus"
"Ca. Nitrosocaldus"
"Ca. Nitrosomirus"
"Ca. Nitrosotalea"
"Ca. Nitrosotenuis"
"Ca. Nitrosopelagicus"
"Cenarchaeum "
"Ca. Nitrosoabyssus"