# Haloferax

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Genus of archaea

Haloferax SEM image of Haloferax mediterranei. Scientific classification Domain: Archaea Kingdom: Methanobacteriati Phylum: Methanobacteriota Class: Halobacteria Order: Haloferacales Family: Haloferacaceae Genus: Haloferax Torreblanca et al. 1986[1] Type species Haloferax volcanii (Mullakhanbhai & Larsen 1975) Torreblanca et al. 1986 Species See text

***Haloferax*** (common abbreviation: ***Hfx.***) is a genus of halobacteria in the order [Haloferacaceae](/source/Haloferacaceae).[2]

## Genetic exchange

Cells of *H. mediterranei* and cells of the related species *[H. volcanii](/source/Haloferax_volcanii)* can undergo a process of genetic exchange between two cells which involves cell fusion resulting in a heterodiploid cell (containing two different chromosomes in one cell).[3] Although this genetic exchange ordinarily occurs between two cells of the same species, it can also occur at a lower frequency between an *H. mediterranei* and an *H. volcani* cell. These two species have an average nucleotide sequence identity of 86.6%.[3] During this exchange process, a diploid cell is formed that contains the full genetic repertoire of both parental cells, and genetic recombination is facilitated. Subsequently, the cells separate, giving rise to recombinant cells.

## Taxonomy

As of 2022, 13 species are validly published under the genus *Haloferax*.[1]

**Proposed species**

Several species and novel binomial names have been proposed, but not validly published.

- "*Haloferax antrum*" Enache et al. 2006,[4] "*Haloferax opilio*" Enache et al. 2006, "*Haloferax rutilus*" Enache et al. 2006 and "*Haloferax viridis*" Enache et al. 2006 were isolated from [Romanian](/source/Romania) salt lakes and first proposed as new species in 2006.[5] Only *[H. prahovense](/source/Haloferax_prahovense)*, that was proposed along them has since been validly published.

- "*Haloferax berberensis*" Kharroub et al. 2005e was isolated in [Algeria](/source/Algeria) and proposed as new species in 2005.[6]

- *Haloferax litoreum*, *Haloferax marinisediminis* and *Haloferax marinum* were first published in 2021, but are not accepted as of 2022.[7]

- *Haloferax marisrubri* and *Haloferax profundi* were first published in 2020, but is not accepted as of 2022.[8]

- *Haloferax massilisiensis* or *Haloferax massiliense* was first published in 2016 and again in 2018 as human associated halophilic archaeon. As of 2022, this species is not accepted.[9]

### Phylogeny

The currently accepted taxonomy is based on the [List of Prokaryotic names with Standing in Nomenclature](/source/List_of_Prokaryotic_names_with_Standing_in_Nomenclature) (LPSN)[1] and [National Center for Biotechnology Information](/source/National_Center_for_Biotechnology_Information) (NCBI).[2]

16S rRNA based LTP_10_2024[10][11][12] 53 marker proteins based GTDB 10-RS226[13][14][15] Haloferax H. namakaokahaiae McDuff et al. 2017 H. elongans H. larsenii H. sulfurifontis Elshahed et al. 2004 H. mediterranei H. mucosum H. chudinovii Saralov et al. 2014 H. denitrificans H. lucentense corrig. Gutierrez et al. 2004 H. gibbonsii H. prahovense H. alexandrinus Asker & Ohta 2002 H. volcanii Haloferax H. elongans Allen et al. 2008 H. larsenii Xu et al. 2007 H. litoreum Cho et al. 2025 "H. profundi" Zhang et al. 2020 H. marinisediminis Cho et al. 2025 H. marinum Cho et al. 2025 H. mediterranei (Rodriguez-Valera et al. 1983) Torreblanca et al. 1987 H. mucosum Allen et al. 2008 H. gibbonsii Juez et al. 1986 H. prahovense Enache et al. 2007 "H. marisrubri" Zhang et al. 2020 H. denitrificans (Tomlinson et al. 1986) Tindall et al. 1989 [incl. H. sulfurifontis] "H. massiliensis" Khelaifia & Raoult 2016 H. volcanii (Mullakhanbhai & Larsen 1975) Torreblanca et al. 1986 [incl. H. alexandrinus, H. lucentense]

Unassigned *Haloferax*:

- "*H. antrum*" Enache et al. 2006

- "*H. berberensis*" Kharroub et al. 2005e

- "*H. opilio*" Enache et al. 2006

- "*H. rutilus*" Enache et al. 2006

- "*H. viridis*" Enache et al. 2006

## Industrial biotechnology

Several *Haloferax* species, especially *Haloferax mediterranei* have gained eminence for their ability to serve as an efficient chassis for bioproduction. *H. mediterranei* is a well-known producer of [polyhydroxyalkanoates](/source/Polyhydroxyalkanoates), a sustainable and biodegradable bioplastic.[16] They have been studied for the production of several value-added products such as bioplastics, pigments and exoenzymes.[17] *H. mediterranei* is capable of accumulating high amounts of both homopolymer PHAs and co-polymer PHAs from a wide array of sustainable carbon substrates.[16][18] *Haloferax* species have also been used to produce industrially relevant exoenzymes such as laccase for bioprocessing.[19] Since they can thrive in extreme conditions of salinity, toxicity, [heavy metal](/source/Heavy_metals) exposure and UV radiation, the fermentation costs are significantly lowered as the chance of contamination is reduced.[17] In hypersaline environments like the [Dead Sea](/source/Dead_Sea) & [Great Salt Lake](/source/Great_Salt_Lake), *Haloferax* species shoulder most of the responsibility of [denitrification](/source/Denitrification).[20] These strains could be leveraged for nitrogen removal systems designed to remediate saline effluents from fisheries, textile industries and food processing plants.

## See also

- [Archaea](/source/Archaea)

- [List of Archaea genera](/source/List_of_Archaea_genera)

- [Homologous recombination](/source/Homologous_recombination)

- [Extremophile](/source/Extremophile)

## References

1. ^ [***a***](#cite_ref-LPSN_1-0) [***b***](#cite_ref-LPSN_1-1) [***c***](#cite_ref-LPSN_1-2) J.P. Euzéby. ["Haloferax"](https://lpsn.dsmz.de/genus/haloferax). [List of Prokaryotic names with Standing in Nomenclature](/source/List_of_Prokaryotic_names_with_Standing_in_Nomenclature) (LPSN). Retrieved 2023-10-10.

1. ^ [***a***](#cite_ref-NCBI_2-0) [***b***](#cite_ref-NCBI_2-1) Sayers; et al. ["Haloferax"](https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?command=show&mode=tree&id=2251&lvl=3). [National Center for Biotechnology Information](/source/National_Center_for_Biotechnology_Information) (NCBI) taxonomy database. Retrieved 2023-10-10.

1. ^ [***a***](#cite_ref-pmid22748314_3-0) [***b***](#cite_ref-pmid22748314_3-1) Naor A, Lapierre P, Mevarech M, Papke RT, Gophna U (August 2012). ["Low species barriers in halophilic archaea and the formation of recombinant hybrids"](https://doi.org/10.1016%2Fj.cub.2012.05.056). *Curr. Biol*. **22** (15): 1444–8. [Bibcode](/source/Bibcode_(identifier)):[2012CBio...22.1444N](https://ui.adsabs.harvard.edu/abs/2012CBio...22.1444N). [doi](/source/Doi_(identifier)):[10.1016/j.cub.2012.05.056](https://doi.org/10.1016%2Fj.cub.2012.05.056). [PMID](/source/PMID_(identifier)) [22748314](https://pubmed.ncbi.nlm.nih.gov/22748314).

1. **[^](#cite_ref-ENA_(H.antrum)_4-0)** [*EBA - European Nucleotide Archive*](https://www.ebi.ac.uk/ena/browser/view/AB258308), retrieved 2022-07-14

1. **[^](#cite_ref-NCBI_(Enache_2006)_5-0)** [*NCBI Taxonomy browser (Haloferax antrum)*](https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&id=381855), retrieved 2022-07-14

1. **[^](#cite_ref-NCBI_(H.berberensis)_6-0)** [*NCBI Taxonomy browser (Haloferax berberensis)*](https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&id=340952), retrieved 2022-07-14

1. **[^](#cite_ref-LPSN_(Cho_2021)_7-0)** ["LPSN - List of Prokaryotic names with Standing in Nomenclature"](https://lpsn.dsmz.de/species/haloferax-litoreum). [Deutsche Sammlung von Mikroorganismen und Zellkulturen](/source/Deutsche_Sammlung_von_Mikroorganismen_und_Zellkulturen). Retrieved 2022-07-14.

1. **[^](#cite_ref-LPSN_(H.marisrubri_Zhang_2020)_8-0)** ["LPSN - List of Prokaryotic names with Standing in Nomenclature"](https://lpsn.dsmz.de/species/haloferax-marisrubri). [Deutsche Sammlung von Mikroorganismen und Zellkulturen](/source/Deutsche_Sammlung_von_Mikroorganismen_und_Zellkulturen). Retrieved 2022-07-14.

1. **[^](#cite_ref-LPSN_(H.massiliense_Khelaifa&Raoult_2026)_9-0)** ["LPSN - List of Prokaryotic names with Standing in Nomenclature"](https://lpsn.dsmz.de/species/haloferax-massiliensis). [Deutsche Sammlung von Mikroorganismen und Zellkulturen](/source/Deutsche_Sammlung_von_Mikroorganismen_und_Zellkulturen). Retrieved 2022-07-14.

1. **[^](#cite_ref-10)** ["The LTP"](https://imedea.uib-csic.es/mmg/ltp/#LTP). Retrieved 10 December 2024.

1. **[^](#cite_ref-11)** ["LTP_all tree in newick format"](https://imedea.uib-csic.es/mmg/ltp/wp-content/uploads/ltp/LTP_all_10_2024.ntree). Retrieved 10 December 2024.

1. **[^](#cite_ref-12)** ["LTP_10_2024 Release Notes"](https://imedea.uib-csic.es/mmg/ltp/wp-content/uploads/ltp/LTP_10_2024_release_notes.pdf) (PDF). Retrieved 10 December 2024.

1. **[^](#cite_ref-about_13-0)** ["GTDB release 10-RS226"](https://gtdb.ecogenomic.org/about#4%7C). *[Genome Taxonomy Database](/source/Genome_Taxonomy_Database)*. Retrieved 1 May 2025.

1. **[^](#cite_ref-tree_14-0)** ["ar53_r226.sp_label"](https://data.gtdb.ecogenomic.org/releases/release226/226.0/auxillary_files/ar53_r226.sp_labels.tree). *[Genome Taxonomy Database](/source/Genome_Taxonomy_Database)*. Retrieved 1 May 2025.

1. **[^](#cite_ref-taxon_history_15-0)** ["Taxon History"](https://gtdb.ecogenomic.org/taxon_history/). *[Genome Taxonomy Database](/source/Genome_Taxonomy_Database)*. Retrieved 1 May 2025.

1. ^ [***a***](#cite_ref-:0_16-0) [***b***](#cite_ref-:0_16-1) Parroquin-Gonzalez, Mariana; Winterburn, James (2023-09-13). ["Continuous bioreactor production of polyhydroxyalkanoates in Haloferax mediterranei"](https://doi.org/10.3389%2Ffbioe.2023.1220271). *Frontiers in Bioengineering and Biotechnology*. **11** 1220271. [doi](/source/Doi_(identifier)):[10.3389/fbioe.2023.1220271](https://doi.org/10.3389%2Ffbioe.2023.1220271). [ISSN](/source/ISSN_(identifier)) [2296-4185](https://search.worldcat.org/issn/2296-4185).

1. ^ [***a***](#cite_ref-:1_17-0) [***b***](#cite_ref-:1_17-1) Griffiths, Dana B.; Tiwari, Ravi P.; Murphy, Daniel V.; Scott, Colin (November 2025). "Haloferax and the Haloferacaceae: Potential role in bioindustry". *Biotechnology Advances*. **84** 108666. [doi](/source/Doi_(identifier)):[10.1016/j.biotechadv.2025.108666](https://doi.org/10.1016%2Fj.biotechadv.2025.108666). [ISSN](/source/ISSN_(identifier)) [1873-1899](https://search.worldcat.org/issn/1873-1899). [PMID](/source/PMID_(identifier)) [40744239](https://pubmed.ncbi.nlm.nih.gov/40744239).

1. **[^](#cite_ref-18)** Wang, Ke; Zhang, Ruihong (2021-02-28). ["Production of Polyhydroxyalkanoates (PHA) by Haloferax mediterranei from Food Waste Derived Nutrients for Biodegradable Plastic Applications"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9706037). *Journal of Microbiology and Biotechnology*. **31** (2): 338–347. [doi](/source/Doi_(identifier)):[10.4014/jmb.2008.08057](https://doi.org/10.4014%2Fjmb.2008.08057). [ISSN](/source/ISSN_(identifier)) [1738-8872](https://search.worldcat.org/issn/1738-8872). [PMC](/source/PMC_(identifier)) [9706037](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9706037). [PMID](/source/PMID_(identifier)) [33203825](https://pubmed.ncbi.nlm.nih.gov/33203825).

1. **[^](#cite_ref-19)** Kasirajan, Lakshmi; Adams, Zachary; Couto-Rodriguez, Ricardo L.; Gal, Daniel; Jia, Huiyong; Mondragon, Paula; Wassel, Paul C.; Yu, David; Uthandi, Sivakumar; Maupin-Furlow, Julie A. (2021). "High-level synthesis and secretion of laccase, a metalloenzyme biocatalyst, by the halophilic archaeon Haloferax volcanii". *Recombinant Protein Expression: Prokaryotic Hosts and Cell-Free Systems*. Methods in Enzymology. Vol. 659. pp. 297–313. [doi](/source/Doi_(identifier)):[10.1016/bs.mie.2021.05.012](https://doi.org/10.1016%2Fbs.mie.2021.05.012). [ISBN](/source/ISBN_(identifier)) [978-0-323-90146-8](https://en.wikipedia.org/wiki/Special:BookSources/978-0-323-90146-8). [ISSN](/source/ISSN_(identifier)) [1557-7988](https://search.worldcat.org/issn/1557-7988). [PMC](/source/PMC_(identifier)) [8867731](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8867731). [PMID](/source/PMID_(identifier)) [34752290](https://pubmed.ncbi.nlm.nih.gov/34752290).

1. **[^](#cite_ref-20)** Torregrosa-Crespo, Javier; Pire, Carmen; Martínez-Espinosa, Rosa María; Bergaust, Linda (2019). ["Denitrifying haloarchaea within the genus Haloferax display divergent respiratory phenotypes, with implications for their release of nitrogenous gases"](https://onlinelibrary.wiley.com/doi/abs/10.1111/1462-2920.14474). *Environmental Microbiology*. **21** (1): 427–436. [Bibcode](/source/Bibcode_(identifier)):[2019EnvMi..21..427T](https://ui.adsabs.harvard.edu/abs/2019EnvMi..21..427T). [doi](/source/Doi_(identifier)):[10.1111/1462-2920.14474](https://doi.org/10.1111%2F1462-2920.14474). [ISSN](/source/ISSN_(identifier)) [1462-2920](https://search.worldcat.org/issn/1462-2920).

## Further reading

- Oren A, Ventosa A (2000). ["International Committee on Systematic Bacteriology Subcommittee on the taxonomy of Halobacteriaceae. Minutes of the meetings, 16 August 1999, Sydney, Australia"](https://doi.org/10.1099%2F00207713-50-3-1405). *Int. J. Syst. Evol. Microbiol*. **50** (3): 1405–1407. [doi](/source/Doi_(identifier)):[10.1099/00207713-50-3-1405](https://doi.org/10.1099%2F00207713-50-3-1405). [PMID](/source/PMID_(identifier)) [10843089](https://pubmed.ncbi.nlm.nih.gov/10843089).

- Torreblanca M, Rodriquez-Valera F, Juez G, Ventosa A, Kamekura M, Kates M (1986). "Classification of non-alkaliphilic halobacteria based on numerical taxonomy and polar lipid composition, and description of Haloarcula gen. nov. and Haloferax gen.nov". *Syst. Appl. Microbiol*. **8** (1–2): 89–99. [Bibcode](/source/Bibcode_(identifier)):[1986SyApM...8...89T](https://ui.adsabs.harvard.edu/abs/1986SyApM...8...89T). [doi](/source/Doi_(identifier)):[10.1016/s0723-2020(86)80155-2](https://doi.org/10.1016%2Fs0723-2020%2886%2980155-2).

- Gibbons, NE (1974). "Family V. Halobacteriaceae fam. nov.". In RE Buchanan; NE Gibbons (eds.). [*Bergey's Manual of Determinative Bacteriology*](https://archive.org/details/bergeysmanualofd00atio) (8th ed.). Baltimore: The Williams & Wilkins Co. [ISBN](/source/ISBN_(identifier)) [0-683-01117-0](https://en.wikipedia.org/wiki/Special:BookSources/0-683-01117-0).

## External links

- [*Haloferax* at Bac*Dive* - the Bacterial Diversity Metadatabase](http://bacdive.dsmz.de/index.php?search=Haloferax&submit=Search)

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Taxon identifiers Haloferax Wikidata: Q3126194 Wikispecies: Haloferax EoL: 97527 GBIF: 1000195 IRMNG: 1307680 ITIS: 951505 LPSN: haloferax NCBI: 2251 Open Tree of Life: 517052 SeqCode Registry: 8899 WoRMS: 559472

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Adapted from the Wikipedia article [Haloferax](https://en.wikipedia.org/wiki/Haloferax) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Haloferax?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.