Nanobdellota

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Nanobdellota (previously "Nanoarchaeota",<ref>Template:Cite journal</ref> Greek for "dwarf or tiny ancient one") is a phylum of Archaea.<ref>See the NCBI webpage on Nanoarchaeota. Data extracted from the Template:Cite web</ref> The first species discovered, Nanoarchaeum equitans, was from a submarine hydrothermal vent in Iceland and described in 2002.<ref name="Huber-2002" /> The name of the phylum is derived from the species Nanobdella (Greek nânos, a dwarf; bdella, leech) aerobiophila discovered from a terrestrial hot spring in Japan.

Discovery and taxonomy

By the end of the 1990s, three groups of Archaea were recognised: Crenarchaeota, Euryarchaeota and Korarchaeota. The groups were variously designated as kingdoms or phyla.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> In 2002, Harald Huber and his colleagues at the University of Regensburg and Max Planck Institute for Medical Research discovered a new archaea from a submarine hot vent in Iceland.<ref>Template:Cite journal</ref> The species could not be fitted into any of the known groups so that they created a new phylum "Nanoarchaeota" for the new species they named Nanoarchaeum equitans.<ref>Template:Cite journal</ref>

In 2022, Japanese scientists led by Shingo Kato described a new species Nanobdella aerobiophila discovered from a terrestrial hot spring in Japan. For the classification, they created family Nanobdellaceae, order Nanobdellales and class Nanobdellia.<ref>Template:Cite journal</ref> In 2023, they introduced a new phylum Nanobdellota for the species.<ref>Template:Citation</ref> According to the revised International Code of Nomenclature of Prokaryotes (ICNP, Prokaryotic Code) of 2022, the name of a taxon cannot be created using the same spelling of the stem taxon, genus name, which is not validly published. Nanoarchaeota was not a validly published name while Nanobdella is a valid name and<ref>Template:Cite journal</ref> thus, Nanobdellota is accepted as the correct name of the phylum, and a new kingdom Nanobdellati was created in 2023.<ref>Template:Cite journal</ref><ref name=":0">Template:Cite journal</ref>

Species and diversity

Members of the Nanobdellota are associated with different host organisms and environmental conditions.<ref name="Munson-McGee 7860–7868">Template:Cite journal</ref> Despite small size, a reduced genome and limited respiration, they have unusual metabolic features. For example, N. equitans has a complex and highly developed intercellular communication system.<ref>Template:Cite journal</ref>

The phylogeny of the Nanobdellota is anchored by its only cultured representative, Nanoarchaeum equitans, which clusters in a separate evolutionary group than other archaea,<ref>Template:Cite journal</ref><ref name="Waters-2003">Template:Cite journal</ref> which have recently been reclassified. Further analysis has shown that N. equitans diverged early on in the evolution of Archaea, as indicated by the 16S rRNA sequence. This suggests that they occupy a deeply branching position within this group.<ref>Template:Cite book</ref>

The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN)<ref>Template:Cite web</ref> and the National Center for Biotechnology Information (NCBI).<ref>Template:Cite web</ref>

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  • Class Nanobdellia Kato et al. 2022<ref name="Kato-2022">Template:Cite journal</ref> ["Nanoarchaea" Huber et al. 2011;<ref name="Wiley-2015">Template:Cite book</ref> "Nanoarchaeia" Vazquez-Campos et al. 2021<ref name="Vázquez-Campos-2021"/>]
    • Order "Tiddalikarchaeales" Vazquez-Campos et al. 2021<ref name="Vázquez-Campos-2021">Template:Cite journal</ref>
      • Family "Tiddalikarchaeaceae" Vazquez-Campos et al. 2021<ref name="Vázquez-Campos-2021"/>
        • Genus "Candidatus Tiddalikarchaeum" Vazquez-Campos et al. 2021<ref name="Vázquez-Campos-2021"/>
          • "Ca. T. anstoanum" Vazquez-Campos et al. 2021<ref name="Vázquez-Campos-2021"/>
    • Order "Jingweiarchaeales" Rao et al. 2023
      • Family "Jingweiarchaeaceae" Rao et al. 2023
        • Genus "Candidatus Jingweiarchaeum" Rao et al. 2023
          • "Ca. J. tengchongense" Rao et al. 2023
    • Order "Parvarchaeales" Rinke et al. 2020<ref name="Rinke-2021"/>
      • Family "Parvarchaeaceae" Rinke et al. 2020<ref name="Rinke-2021" /> ["Acidifodinimicrobiaceae" Luo et al. 2020<ref name="Luo-2020">Template:Cite journal</ref>]
        • Genus "Candidatus Rehaiarchaeum" Rao et al. 2023
          • "Ca. R. fermentans" Rao et al. 2023
        • Genus "Candidatus Acidifodinimicrobium" Luo et al. 2020<ref name="Luo-2020"/>
          • "Ca. A. mancum" Luo et al. 2020<ref name="Luo-2020"/>
        • Genus "Candidatus Parvarchaeum" Baker et al. 2010<ref name="Baker-2010">Template:Cite journal</ref>
          • "Ca. P. acidiphilum" Baker et al. 2010<ref name="Baker-2010" />
          • "Ca. P. paracidiphilum" corrig. Baker et al. 2010<ref name="Baker-2010" />
          • "Ca. P. tengchongense" Rao et al. 2023
    • Order Nanobdellales Kato et al. 2022<ref name="Kato-2022"/> [Nanoarchaeales Huber et al. 2011<ref name="Wiley-2015"/>]
      • Family "Nanoarchaeaceae" Huber et al. 2011<ref name="Wiley-2015"/>
      • Family Nanobdellaceae Kato et al. 2022<ref name="Kato-2022"/> ["Nanopusillaceae" Huber et al. 2011<ref name="Wiley-2015"/>]
        • Genus Nanobdella Kato et al. 2022<ref name="Kato-2022"/>
          • N. aerobiophila Kato et al. 2022<ref name="Kato-2022"/>
        • Genus "Candidatus Nanoclepta" St. John et al. 2019<ref name="St. John-2019">Template:Cite journal</ref>
          • "Ca. N. minuta" St. John et al. 2019<ref name="St. John-2019"/>
        • Genus "Candidatus Nanopusillus" Wurch et al. 2016<ref name="Wurch-2016">Template:Cite journal</ref>
          • "Ca. N. acidilobi" Wurch et al. 2016<ref name="Wurch-2016"/>
          • ?"Ca. N. massiliensis" Hassani et al. 2022
          • ?"Ca. N. phoceensis" Hassani et al. 2024
          • "Ca. N. stetteri" (Castelle et al. 2015) Rinke et al. 2020<ref name="Rinke-2021">Template:Cite journal</ref>
    • Family "Haiyanarchaeaceae" Rao et al. 2023
      • Genus "Candidatus Haiyanarchaeum" Rao et al. 2023
        • "Ca. H. thermophilum" Rao et al. 2023
Nanoarchaeum equitans

Characteristics

Cells of N. equitans are spherical with a diameter of approximately 400 nm,<ref name="Huber-2002"/> and have a very short and compact DNA sequence with the entire genome containing only 490,885 base pairs.<ref name="Waters-2003" /> While they have the genetic code to carry out processing and repair, they cannot carry out certain biosynthetic and metabolic processes such as lipid, amino-acid, cofactor, or nucleotide synthesis.<ref name="Waters-2003" /> Due to its limited machinery, it is an obligate parasite, the only one known in the Archaea.<ref name="Waters-2003" /> Because of their unusual ss rRNA sequences, they are difficult to detect using standard polymerase chain reaction methods.<ref name="Huber-2002-2">Template:Cite journal</ref> Cells of N. equitans contain a normal S-layer with sixfold symmetry with a 15 nm lattice constant.<ref name="Huber-2002-2" />

Genome structure

Small cells between 100 and 400 nm in diameter and highly streamlined genomes of 0.491-0.606 Mbp characterize nanoarchaeotes.<ref name="St John Reysenbach Nanoarchaeota">Template:Cite book</ref> The genomes of described nanoarchaeotes demonstrate different degrees of reduction, which is compatible with a host dependent lifestyle.<ref name="St John Reysenbach Nanoarchaeota"/> Certain nanaoarchaeotes still have genes for the CRISPR-Cas systems, archaeal flagella, and the gluconeogenesis pathway.<ref name="St John Reysenbach Nanoarchaeota"/>

Habitat

Nanoarchaeotes are obligate symbionts that grow attached to an archaeal host known as Ignicoccus.<ref>Template:Citation</ref> Both terrestrial hot springs and underwater hydrothermal vents have yielded isolates in the genus Nanoarchaeum .<ref name="Amils 2011 1106–1106">Template:Citation</ref> However, there is evidence that nanoarcheotes reside in a variety of habitats outside of marine thermal vents.<ref name="Munson-McGee 7860–7868" />  Genetic evidence for members of the Nanoarchaeota has been discovered to be pervasive in terrestrial hot springs and mesophilic hypersaline habitats using primers created based on the sequence of the 16S rRNA gene of Nanoarchaeum equitans.<ref name="Munson-McGee 7860–7868" /> In addition, the discovery of ribosomal sequences in photic-zone water samples taken distant from hydrothermal vents raises the possibility that Nanoarchaeota are an ubiquitous and diversified group of Archaea that can live in habitats with a variety of temperatures and geochemical settings.<ref name="Munson-McGee 7860–7868" />

Metabolism

Although much of the metabolism of members of the Nanoarchaeota is unknown, its host is an autotroph that grows on elemental sulphur as an electron acceptor and H2 as an electron donor.<ref name="Amils 2011 1106–1106"/> The majority of recognized metabolic processes, such as the creation of monomers like amino acids, nucleotides, and coenzymes, lack recognizable genes in this organism.<ref name="Amils 2011 1106–1106"/>

See also

References

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Further reading

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