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.[4]
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.[5][6][7]
Taxonomy
The phylum Deinococcota consists of a single class (Deinococci) and two orders:
Though these two groups evolved from a common ancestor, the two mechanisms of resistance appear to be largely independent.[11][15]
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.[4][11] 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.[11] The CSIs found in DNA-directed RNA polymerase subunit beta and DNA topoisomerase I in Thermales species may be involved in thermophilicity,[16] while those found in Excinuclease ABC, DNA gyrase, and DNA repair protein RadA in Deinococcales species may be associated with radioresistance.[17] 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.[11] These CSPs include the DNA damage repair protein PprA the single-stranded DNA-binding protein DdrB.
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.[11] CSIs have also been found specific for Truepera radiovictrix .
Currently there are 10 sequenced genomes of strains in this phylum.[26]
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.[27]
^Garrity GM, Holt JG. (2001). "The Road Map to the Manual". In Boone DR, Castenholz RW, Garrity GM. (eds.). Bergey's Manual of Systematic Bacteriology. Vol. 1 (The Archaea and the deeply branching and phototrophic Bacteria) (2nd ed.). New York, NY: Springer–Verlag. pp. 119–166.
^ abGarrity 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.
^ abGarrity 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.
^ abcdefgHo J, Adeolu M, Khadka B, Gupta RS (2016). "Identification of distinctive molecular traits that are characteristic of the phylum "Deinococcus–Thermus" and distinguish its main constituent groups". Syst Appl Microbiol. 39 (7): 453–463. doi:10.1016/j.syapm.2016.07.003. PMID27506333.
^Battista JR, Earl AM, Park MJ (1999). "Why is Deinococcus radiodurans so resistant to ionizing radiation?". Trends Microbiol. 7 (9): 362–5. doi:10.1016/S0966-842X(99)01566-8. PMID10470044.
^Nelson RM, Long GL (1989). "A general method of site-specific mutagenesis using a modification of the Thermus aquaticus". Anal Biochem. 180 (1): 147–151. doi:10.1016/0003-2697(89)90103-6. PMID2530914.
