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Haloferacales
Scientific classification
Domain:	Archaea
Kingdom:	Euryarchaeota
Class:	Halobacteria
Order:	Haloferacales Gupta et al. 2015
Families
Haloferacaceae Halorubraceae

Haloferacales is an order of halophilic, chemoorganotrophic or heterotrophic archaea within the class Haloarchaea. The type genus of this order is Haloferax.

The name Haloferacales is derived from the Latin term Haloferax, referring to the type genus of the order and the suffix "-ales," an ending used to denote an order. Together, Haloferacales refers to an order whose nomenclatural type is the genus Haloferax.

Biochemical characteristics and molecular signatures

Members are halophiles and can be chemoorganotrophs or heterotrophs and are isolated from high-salt environments such as marine solar salterns and the Dead Sea. Some members are motile and contain gas vesicles. Morphology is variable, including rod, coccus or flat square shapes. Members of this order grow optimally in neutral pH. The DNA G+C content for this order ranges between 55-66 mol%.

This order can be reliably distinguished from other Halobacteria by the presence of five conserved signature proteins (CSPs) and four conserved signature indels (CSIs) present in the following proteins: DNA gyrase B, prolyl t-RNA synthetase, acyl-CoA synthetase and aspartyl/glutamyl-tRNA amido-transferase subunit B.

Historical systematics and current taxonomy

As of 2021, Haloferacales contains two families, Haloferacaceae and Halorubraceae. Members of this order was demarcated from the class Halobacteria, previously a large phylogenetically unrelated group of species with distinct biochemical characteristics and different ecological niches. The diverse range of morphological and physiological characteristics made it difficult to clarify the evolutionary relationship within the class beyond a genus level.

In 2015, Gupta et al. proposed the division of the class Halobacteria into the orders Halobacteriales, Haloferacales and Natrialbales based on comparative genomic analyses and the branching pattern of various phylogenetic trees constructed from several different datasets of conserved proteins and 16S rRNA sequences. Molecular markers, specifically conserved signature indels, specific to this order were also identified as evidence supporting the division independent of phylogenetic trees. Each order can be reliably distinguished from each other and other species based on the presence of these CSIs.

Phylogeny

The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN) and National Center for Biotechnology Information (NCBI).

See also

• List of Archaea genera

References

1. ^ Sayers; et al. "Haloferacales". National Center for Biotechnology Information (NCBI) taxonomy database. Retrieved 2023-05-17.
2. ^ J.P. Euzéby. "Haloferacales". List of Prokaryotic names with Standing in Nomenclature (LPSN). Retrieved 2023-05-17.
3. ^ Gupta, Radhey S.; Naushad, Sohail; Baker, Sheridan (2015-03-01). "Phylogenomic analyses and molecular signatures for the class Halobacteria and its two major clades: a proposal for division of the class Halobacteria into an emended order Halobacteriales and two new orders, Haloferacales ord. nov. and Natrialbales ord. nov., containing the novel families Haloferacaceae fam. nov. and Natrialbaceae fam. nov". International Journal of Systematic and Evolutionary Microbiology. 65 (Pt_3): 1050–1069. doi:10.1099/ijs.0.070136-0. ISSN 1466-5026.
4. ^ "Order: Haloferacales". lpsn.dsmz.de. Retrieved 2021-06-27.
5. Grant, William D.; Kamekura, Masahiro; McGenity, Terry J.; Ventosa, Antonio (2015-09-14). "Halobacteria class. nov". Bergey's Manual of Systematics of Archaea and Bacteria: 1–1. doi:10.1002/9781118960608.cbm00026.
6. Oren, Aharon (2012-02-01). "Taxonomy of the family Halobacteriaceae: a paradigm for changing concepts in prokaryote systematics". International Journal of Systematic and Evolutionary Microbiology. 62 (2): 263–271. doi:10.1099/ijs.0.038653-0. ISSN 1466-5026.
7. "The LTP". Retrieved 10 May 2023.
8. "LTP_all tree in newick format". Retrieved 10 May 2023.
9. "LTP_06_2022 Release Notes" (PDF). Retrieved 10 May 2023.
10. "GTDB release 08-RS214". Genome Taxonomy Database. Retrieved 10 May 2023.
11. "ar53_r214.sp_label". Genome Taxonomy Database. Retrieved 10 May 2023.
12. "Taxon History". Genome Taxonomy Database. Retrieved 10 May 2023.

• Halobacteria
• Taxa described in 2015