Wikipedia

Halobacteriales

Halobacteriales are an order of the Halobacteria,[1] found in water saturated or nearly saturated with salt. They are also called halophiles, though this name is also used for other organisms which live in somewhat less concentrated salt water. They are common in most environments where large amounts of salt, moisture, and organic material are available. Large blooms appear reddish, from the pigment bacteriorhodopsin. This pigment is used to absorb light, which provides energy to create ATP. Halobacteria also possess a second pigment, halorhodopsin, which pumps in chloride ions in response to photons, creating a voltage gradient and assisting in the production of energy from light. The process is unrelated to other forms of photosynthesis involving electron transport; however, and halobacteria are incapable of fixing carbon from carbon dioxide.

Halobacteriales
SEM image of Haloarcula quadrata.
Scientific classification
Domain:
Archaea
Kingdom:
Euryarchaeota
Phylum:
Euryarchaeota
Class:
Halobacteria
Order:
Halobacteriales

Grant & Larsen, 1989
Families
Synonyms
  • "Haloarchaeales" (sic) DasSarma & DasSarma 2008

Halobacteria can exist in salty environments because although they are aerobes they have a separate and different way of creating energy through photosynthesis. Parts of the membranes of halobacteria are purplish in color. These parts conduct photosynthetic reactions with retinal pigment rather than chlorophyll. This allows them to create a proton gradient across the membrane of the cell which can be used to create ATP for their own use. Some species in this order are used as model organisms to study how some microorganisms can survive in hypersaline environments, understand cellular processes and to research their physiology.[2]

Ecology

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Habitats

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Usually, Halobacteriales grow in aerobic and high salinity environments.[3] Halobacteriales have been found in salt lakes, marine salterns, seawater, solar salts and salted food products.[4] Mostly, members of the order Halobacteriales can be located in environments where concentration of salt (NaCl) exceeds 25%.[2] However, they can also survive in environments with low concentrations of salt, between 1 and 3.5%.[2] Studies show Halobacteriales can also be found in environments where sulfur reduction takes part as well as in salinity salterns,, seawater black smoker, coastal salt marshes and chimney structures.[3] This results show Halobacteriales only need the enough amount of salt to prevent their lysis and thus can grow in environments with low salinity concentration.[3]

Current taxonomy

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Halobacteriales was a large phylogenetically diverse lineage encompassing all Halobacteria species.[4] The wide variety of biochemical characteristics and different ecological niches of the class Haloarchaea proved to be an unreliable tool in clarifying the evolutionary relationships of Halobacteria above the genus level.[4]

In 2015, Gupta et al. proposed the division of class Halobacteria into three 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.[5] This division greatly restricted the membership of the order Halobacteriales to include only species which were closely related to the type genus, Halobacterium.

A subsequent study examining higher taxonomic relationships within the order Halobacteriales resulted in the division of the order into three families, Halobacteriaceae, Haloarculaceae and Halococcaceae, each of which can be distinguished from each other and all other species through the presence of multiple highly specific molecular signatures, known as conserved signature indels.[6]

Phylogeny

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The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN)[7] and National Center for Biotechnology Information (NCBI).[8]

16S rRNA based LTP_06_2022[9][10][11] 53 marker proteins based GTDB 08-RS214[12][13][14]
Halobacteriales

Salinarchaeum {"Salinarchaeaceae"}

Halostella {QS-9-68-17} *

Natronoarchaeum {"Natronoarchaeaceae"} *

Natrialbaceae

Note: * paraphyletic Halobacteriaceae

See also

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References

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  1. ^ See the NCBI webpage on Halobacteriales. Data extracted from the "NCBI taxonomy resources". National Center for Biotechnology Information. Retrieved 2007-03-19.
  2. ^ a b c Youssef NH, Ashlock-Savage KN, Elshahed MS (March 2012). "Phylogenetic diversities and community structure of members of the extremely halophilic Archaea (order Halobacteriales) in multiple saline sediment habitats". Applied and Environmental Microbiology. 78 (5): 1332–44. doi:10.1128/AEM.07420-11. PMC 3294467. PMID 22179255.
  3. ^ a b c Elshahed MS, Najar FZ, Roe BA, Oren A, Dewers TA, Krumholz LR (April 2004). "Survey of archaeal diversity reveals an abundance of halophilic Archaea in a low-salt, sulfide- and sulfur-rich spring". Applied and Environmental Microbiology. 70 (4): 2230–9. doi:10.1128/AEM.70.4.2230-2239.2004. PMC 383155. PMID 15066817.
  4. ^ a b c Oren A, Ventosa A, Kamekura M (2017-09-15). "Halobacteriales". In Whitman WB, Rainey F, Kämpfer P, Trujillo M (eds.). Bergey's Manual of Systematics of Archaea and Bacteria. Chichester, UK: John Wiley & Sons, Ltd. pp. 1–3. doi:10.1002/9781118960608.obm00048.pub2. ISBN 978-1-118-96060-8.
  5. ^ 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. PMID 25428416.
  6. ^ Gupta, Radhey S.; Naushad, Sohail; Fabros, Reena; Adeolu, Mobolaji (April 2016). "A phylogenomic reappraisal of family-level divisions within the class Halobacteria: proposal to divide the order Halobacteriales into the families Halobacteriaceae, Haloarculaceae fam. nov., and Halococcaceae fam. nov., and the order Haloferacales into the families, Haloferacaceae and Halorubraceae fam nov". Antonie van Leeuwenhoek. 109 (4): 565–587. doi:10.1007/s10482-016-0660-2. ISSN 0003-6072. PMID 26837779. S2CID 254231068.
  7. ^ J.P. Euzéby. "Halobacteria". List of Prokaryotic names with Standing in Nomenclature (LPSN). Retrieved 2021-11-17.
  8. ^ Sayers; et al. "Halobacteria". National Center for Biotechnology Information (NCBI) taxonomy database. Retrieved 2022-06-05.
  9. ^ "The LTP". Retrieved 10 May 2023.
  10. ^ "LTP_all tree in newick format". Retrieved 10 May 2023.
  11. ^ "LTP_06_2022 Release Notes" (PDF). Retrieved 10 May 2023.
  12. ^ "GTDB release 08-RS214". Genome Taxonomy Database. Retrieved 10 May 2023.
  13. ^ "ar53_r214.sp_label". Genome Taxonomy Database. Retrieved 10 May 2023.
  14. ^ "Taxon History". Genome Taxonomy Database. Retrieved 10 May 2023.

Further reading

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Journals

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Books

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  • Grant WD, Kamekura M, McGenity TJ, Ventosa A (2001). "Class III. Halobacteria class. nov.". In DR Boone, RW Castenholz (eds.). Bergey's Manual of Systematic Bacteriology Volume 1: The Archaea and the deeply branching and phototrophic Bacteria (2nd ed.). New York: Springer Verlag. p. 169. ISBN 978-0-387-98771-2.
  • Grant WD, Larsen H (1989). "Group III. Extremely halophilic archaeobacteria. Order Halobacteriales ord. nov.". In JT Staley, MP Bryant, N Pfennig, JG Holt (eds.). Bergey's Manual of Systematic Bacteriology, Volume 3 (1st ed.). Baltimore: The Williams & Wilkins Co. p. 169.
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