Nanobdellota (previously"Nanoarchaeota",[1] Greek for "dwarf or tiny ancient one") is aphylum ofArchaea.[2] The first species discovered,Nanoarchaeum equitans, was from a submarinehydrothermal vent in Iceland and described in 2002.[3] The name of the phylum is derived from the speciesNanobdella (Greeknânos, a dwarf;bdella, leech)aerobiophila discovered from a terrestrial hot spring in Japan.
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.[4][5] In 2002, Harald Huber and his colleagues at theUniversity of Regensburg andMax Planck Institute for Medical Research discovered a new archaea from a submarine hot vent in Iceland.[6] 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 namedNanoarchaeum equitans.[7]
In 2022, Japanese scientists led by Shingo Kato described a new speciesNanobdella aerobiophila discovered from a terrestrial hot spring in Japan. For the classification, they created family Nanobdellaceae, order Nanobdellales and class Nanobdellia.[8] In 2023, they introduced a new phylum Nanobdellota for the species.[9] According to the revisedInternational 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 notvalidly published. Nanoarchaeota was not a validly published name whileNanobdella is a valid name and[10] thus, Nanobdellota is accepted as the correct name of the phylum, and a new kingdom Nanobdellati was created in 2023.[11][12]
Members of the Nanobdellota are associated with different host organisms and environmental conditions.[13] 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.[14]
The phylogeny of the Nanobdellota is anchored by its only cultured representative,Nanoarchaeum equitans, which clusters in a separate evolutionary group than other archaea,[15][16] which have recently been reclassified. Further analysis has shown thatN. equitans diverged early on in the evolution of Archaea, as indicated by the16S rRNA sequence. This suggests that they occupy a deeply branching position within this group.[17]
Cells ofN. equitans are spherical with a diameter of approximately 400nm,[3] and have a very short and compact DNA sequence with the entire genome containing only 490,885base pairs.[16] 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, ornucleotide synthesis.[16] Due to its limited machinery, it is an obligate parasite, the only one known in the Archaea.[16] Because of their unusual ss rRNA sequences, they are difficult to detect using standardpolymerase chain reaction methods.[31] Cells ofN. equitans contain a normal S-layer with sixfold symmetry with a 15 nm lattice constant.[31]
Small cells between 100 and 400 nm in diameter and highly streamlined genomes of 0.491-0.606 Mbp characterize nanoarchaeotes.[32] The genomes of described nanoarchaeotes demonstrate different degrees of reduction, which is compatible with a host dependent lifestyle.[32] Certain nanaoarchaeotes still have genes for theCRISPR-Cas systems,archaeal flagella, and thegluconeogenesis pathway.[32]
Nanoarchaeotes are obligate symbionts that grow attached to an archaeal host known asIgnicoccus.[33] Both terrestrial hot springs and underwater hydrothermal vents have yielded isolates in the genusNanoarchaeum .[34] However, there is evidence that nanoarcheotes reside in a variety of habitats outside of marine thermal vents.[13] Genetic evidence for members of the Nanoarchaeota has been discovered to be pervasive in terrestrial hot springs and mesophilichypersaline habitats using primers created based on the sequence of the 16S rRNA gene ofNanoarchaeum equitans.[13] 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.[13]
Although much of the metabolism of members of the Nanoarchaeota is unknown, its host is an autotroph that grows on elemental sulphur as anelectron acceptor and H2 as anelectron donor.[34] The majority of recognized metabolic processes, such as the creation of monomers like amino acids, nucleotides, andcoenzymes, lack recognizable genes in this organism.[34]
^abcdHuber, Harald; Hohn, Michael J.; Rachel, Reinhard; Fuchs, Tanja; Wimmer, Verena C.; Stetter, Karl O. (May 2002). "A new phylum of Archaea represented by a nanosized hyperthermophilic symbiont".Nature.417 (6884):63–67.Bibcode:2002Natur.417...63H.doi:10.1038/417063a.PMID11986665.
^abHuber, Harald; Hohn, Michael J.; Rachel, Reinhard; Fuchs, Tanja; Wimmer, Verena C.; Stetter, Karl O. (2 May 2002). "A new phylum of Archaea represented by a nanosized hyperthermophilic symbiont".Nature.417 (6884):63–67.Bibcode:2002Natur.417...63H.doi:10.1038/417063a.PMID11986665.
^abcSt. John, Emily; Reysenbach, Anna-Louise (2019). "Nanoarchaeota".Reference Module in Life Sciences.doi:10.1016/B978-0-12-809633-8.20766-8.ISBN978-0-12-809633-8.Cultivated nanoarchaeotes are ectosymbionts with small cell diameters (~100–400 nm) and reduced genomes (0.491–0.606 Mbp). Described Nanoarchaeota lack most genes involved in major biosynthetic pathways and likely obtain many cellular products directly from their hosts.
^Huber, Harald; Hohn, Michael J.; Rachel, Reinhard; Stetter, Karl O. (2006), Dworkin, Martin; Falkow, Stanley; Rosenberg, Eugene; Schleifer, Karl-Heinz (eds.), "Nanoarchaeota",The Prokaryotes: Volume 3: Archaea. Bacteria: Firmicutes, Actinomycetes, New York, NY: Springer, pp. 274–280,doi:10.1007/0-387-30743-5_14,ISBN978-0-387-30743-5
^abcAmils, Ricardo (2011), "Nanoarchaeota", in Gargaud, Muriel; Amils, Ricardo; Quintanilla, José Cernicharo; Cleaves, Henderson James (Jim) (eds.),Encyclopedia of Astrobiology, Berlin, Heidelberg: Springer, p. 1106,doi:10.1007/978-3-642-11274-4_1040,ISBN978-3-642-11274-4
Hohn, MJ; Hedlund BP; Huber H (2002). "Detection of 16S rDNA sequences representing the novel phylum 'Nanoarchaeota': indication for a wide distribution in high temperature biotopes".Syst. Appl. Microbiol.25 (4):551–554.doi:10.1078/07232020260517698.PMID12583716.
Huber, Harald; Hohn, Michael J.; Rachel, Reinhard; Fuchs, Tanja; Wimmer, Verena C.; Stetter, Karl O. (2 May 2002). "A new phylum of Archaea represented by a nanosized hyperthermophilic symbiont".Nature.417 (6884):63–67.Bibcode:2002Natur.417...63H.doi:10.1038/417063a.PMID11986665.
Stackebrandt, E; Frederiksen W; Garrity GM; Grimont PA; et al. (2002). "Report of the ad hoc committee for the re-evaluation of the species definition in bacteriology".Int. J. Syst. Evol. Microbiol.52 (Pt 3):1043–1047.doi:10.1099/00207713-52-3-1043.PMID12054223.
Gurtler, V; Mayall BC (2001). "Genomic approaches to typing, taxonomy and evolution of bacterial isolates".Int. J. Syst. Evol. Microbiol.51 (Pt 1):3–16.doi:10.1099/00207713-51-1-3.PMID11211268.
Young, JM (2001). "Implications of alternative classifications and horizontal gene transfer for bacterial taxonomy".Int. J. Syst. Evol. Microbiol.51 (Pt 3):945–53.doi:10.1099/00207713-51-3-945.PMID11411719.
.webp)
