Hadobacteria
| Deinococcus–Thermus | |
|---|---|
| Scientific classification | |
| Domain: | Bacteria |
| Phylum: |
Deinococcus–Thermus Garrity & Holt 2001 |
| Class: | Deinococci |
| Orders & Families | |
| Synonyms | |
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Deinococcus–Thermus is a phylum of bacteria that are highly resistant to environmental hazards, also known as extremophiles. 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.Cavalier-Smith calls this clade Hadobacteria (from Hades, the Greek underworld).
The phylum Deinococcus-Thermus 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.
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 Deinococcus-Thermus phylum. 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. The CSIs found in DNA-directed RNA polymerase subunit beta and DNA topoisomerase I in Thermales species may be involved in thermophilicity, while those found in Excinuclease ABC, DNA gyrase, and DNA repair protein RadA in Deinococcales species may be associated with radioresistance. 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 the single-stranded DNA-binding protein DdrB.
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