Deinococcota

Deinococcota (synonym, "Deinococcus-Thermus") is a phylum of bacteria with a single class, Deinococci, that are highly resistant to environmental hazards, also known as extremophiles.<ref name="pmid18076002">Template:Cite journal</ref>

These bacteria have thick cell walls that give them gram-positive stains, but they include a second membrane and so are closer in structure to those of gram-negative bacteria.<ref name="pmid21717204">Template:Cite journal</ref><ref name="pmid24535491">Template:Cite journal</ref><ref name="pmid20637628">Template:Cite journal</ref>

Taxonomy

The phylum Deinococcota consists of a single class (Deinococci) and two orders:

• The Deinococcales include two families (Deinococcaceae and Trueperaceae), with three genera, Deinococcus, Deinobacterium and Truepera.<ref name="pmid15927420">Template:Cite journal</ref><ref name=Garrity1>Garrity GM, Holt JG. (2001) Phylum BIV. "Deinococcus–Thermus". In: Bergey’s manual of systematic bacteriology, pp. 395-420. Eds D. R. Boone, R. W. Castenholz. Springer-: New York.</ref><ref name=Garrity2>Garrity GM, Bell JA, Lilburn TG. (2005) Phylum BIV. The revised road map to the Manual. In: Bergey’s manual of systematic bacteriology, pp. 159-220. Eds Brenner DJ, Krieg NR, Staley JT, Garrity GM. Springer-: New York.</ref> Truepera radiovictrix is the earliest diverging member of the order.<ref name="pmid15927420"/> Within the order, Deinococcus forms a distinct monophyletic cluster with respect to Deinobacterium and Truepera species.<ref name="pmid27506333">Template:Cite journal</ref> The genus includes several species that are resistant to radiation; they have become famous for their ability to eat nuclear waste and other toxic materials, survive in the vacuum of space and survive extremes of heat and cold.<ref name="pmid10470044">Template:Cite journal</ref>
• The Thermales include several genera resistant to heat (Marinithermus, Meiothermus, Oceanithermus, Thermus, Vulcanithermus, Rhabdothermus) placed within a single family, Thermaceae.<ref name=Garrity1 /><ref name=Garrity2/><ref>Template:Cite web</ref> Phylogenetic analyses demonstrate that within the Thermales, Meiothermus and Thermus species form a monophyletic cluster, with respect to Marinithermus, Oceanithermus, Vulcanithermus and Rhabdothermus that branch as outgroups within the order.<ref name="pmid27506333"/> This suggests that Meiothermus and Thermus species are more closely related to one another relative to other genera within the order. Thermus aquaticus was important in the development of the polymerase chain reaction where repeated cycles of heating DNA to near boiling make it advantageous to use a thermo-stable DNA polymerase enzyme, the Taq polymerase.<ref name="pmid 2530914">Template:Cite journal</ref>

Though these two groups evolved from a common ancestor, the two mechanisms of resistance appear to be largely independent.<ref name="pmid27506333"/><ref name="pmid16242020">Template:Cite journal</ref>

Molecular signatures

Molecular signatures in the form of conserved signature indels (CSIs) and proteins (CSPs) have been found that are uniquely shared by all members belonging to the Deinococcota phylum.<ref name="pmid18076002"/><ref name="pmid27506333"/> These CSIs and CSPs are distinguishing characteristics that delineate the unique phylum from all other bacterial organisms, and their exclusive distribution is parallel with the observed differences in physiology. CSIs and CSPs have also been found that support order and family-level taxonomic rankings within the phylum. Some of the CSIs found to support order level distinctions are thought to play a role in the respective extremophilic characteristics.<ref name="pmid27506333"/> The CSIs found in DNA-directed RNA polymerase subunit beta and DNA topoisomerase I in Thermales species may be involved in thermophilicity,<ref name="pmid 10499798">Template:Cite journal</ref> while those found in Excinuclease ABC, DNA gyrase, and DNA repair protein RadA in Deinococcales species may be associated with radioresistance.<ref name="pmid 15454524">Template:Cite journal</ref>

Additionally, some genera within this group, including Deinococcus, Thermus, and Meiothermus, also have molecular signatures that demarcate them as individual genera, inclusive of their respective species, providing a means to distinguish them from the rest of the group and all other bacteria.<ref name="pmid27506333"/> Two CSPs that were found uniquely for all members belonging to the Deinococcus genus are well characterized and are thought to play a role in their characteristic radioresistant phenotype. These CSPs include the DNA damage repair protein PprA and the single-stranded DNA-binding protein DdrB.<ref name="pmid27506333"/>

CSIs have also been found specific for Truepera radiovictrix.<ref name="pmid27506333"/>

Phylogeny

16S rRNA based LTP_10_2024<ref>Template:Cite web</ref><ref>Template:Cite web</ref><ref>Template:Cite web</ref>	120 marker proteins based GTDB release 10-RS226<ref name="about">Template:Cite web</ref><ref name="tree_bac">Template:Cite web</ref><ref name="taxon_history">Template:Cite web</ref>

Taxonomy

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

• Phylum Deinococcota Oren and Garrity 2021
  • Class Deinococci Garrity & Holt 2002 ["Deinococcia" Oren, Parte & Garrity 2016 ex Cavalier-Smith 2020; "Thermi" Rinke et al. 2013; "Thermia" Cavalier-Smith 2020]
    • Order Deinococcales Rainey et al. 1997 [Trueperales García-López et al. 2020]
      • Family Deinococcaceae Brooks and Murray 1981 emend. Rainey et al. 1997
        • Genus Deinococcus Brooks and Murray 1981 emend. Rainey et al. 1997
        • Genus Deinobacterium Ekman et al. 2011
      • Family Trueperaceae Rainey et al. 2005
        • Genus Truepera da Costa, Rainey and Albuquerque 2005
    • Order Thermales Rainey and Da Costa 2002
      • Family Thermaceae Da Costa and Rainey 2002
        • Genus Allomeiothermus Jiao et al. 2023
        • Genus Calidithermus Raposo et al. 2019
        • Genus Marinithermus Sako et al. 2003
        • Genus Meiothermus Nobre et al. 1996 emend. Albuquerque et al. 2009
        • Genus Oceanithermus Miroshnichenko et al. 2003 emend. Mori et al. 2004
        • Genus Rhabdothermus Steinsbu et al. 2011
        • Genus Thermus Brock and Freeze 1969 emend. Nobre et al. 1996
        • Genus Vulcanithermus Miroshnichenko et al. 2003

Sequenced genomes

Currently there are 10 sequenced genomes of strains in this phylum.<ref>Template:Cite web</ref>

• Deinococcus radiodurans R1
• Thermus thermophilus HB27
• Thermus thermophilus HB8
• Deinococcus geothermalis DSM 11300
• Deinococcus deserti VCD115
• Meiothermus ruber DSM 1279
• Meiothermus silvanus DSM 9946
• Truepera radiovictrix DSM 17093
• Oceanithermus profundus DSM 14977

The two Meiothermus species were sequenced under the auspices of the Genomic Encyclopedia of Bacteria and Archaea project (GEBA), which aims at sequencing organisms based on phylogenetic novelty and not on pathogenicity or notoriety.<ref>Template:Cite journal</ref>

See also

• List of bacteria genera
• List of bacterial orders