Haloarcula

Haloarcula (common abbreviation Har.) is a genus of extreme halophilic Archaea in the class of Halobacteria.^[2]

Haloarcula
SEM image of Haloarcula quadrata.
Scientific classification
Domain:	Archaea
Kingdom:	Methanobacteriati
Phylum:	Methanobacteriota
Class:	Halobacteria
Order:	Halobacteriales
Family:	Haloarculaceae
Genus:	Haloarcula Torreblanca et al. 1986 emend. Ma et al. 2024[1]
Type species
Haloarcula vallismortis (Gonzalez, Gutierrez & Ramirez 1979) Torreblanca et al. 1986
Species
See text

Cell structure

Haloarcula species can be distinguished from other genera in the family Halobacteriaceae by the presence of specific derivatives of TGD-2 polar lipids. H. quadrata has predominantly flat, square-shaped, somewhat pleomorphic cells.^[3]

Metabolism

Haloarcula quadrata was first isolated when researchers were attempting to culture Haloquadratum walsbyi, a haloarchaeon that was thought to be unculturable until 2004. Similar to other halophilic archaea, Haloarcula species grow optimally at 40–45 °C. Growth appears in sheets of up to 65 cells often in the shape of a square or triangle.

Taxonomy

The genus of Haloarcula was long grouped with other halophilic archaea such as Halobacterium until genomic analysis prompted to reorder this genus in the new family of Haloarculaceae.

Phylogeny

The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN)^[4] and National Center for Biotechnology Information (NCBI).^[1]

16S rRNA based LTP_10_2024[5][6][7]

53 marker proteins based GTDB 09-RS220[8][9][10]

Halomicroarcula 2 Halomicroarcula 3 Halomicroarcula 4 Haloarcula H. mannanilytica H. terrestris Straková et al. 2023 H. sebkhae H. tradensis Namwong et al. 2011 H. salaria Namwong et al. 2011 H. amylolytica H. japonica H. hispanica H. argentinensis H. quadrata Oren et al. 1999 H. marismortui H. vallismortis

Halomicrobium Halomicroarcula Haloarcula H. salina (Zhang & Cui 2015) Ma et al. 2023 "H. rubripromontorii" Sanchez-Nieves et al. 2016 "H. taiwanensis" Chen et al. 2018 H. vallismortis (Gonzalez, Gutierrez & Ramirez 1979) Torreblanca et al. 1986 H. mannanilytica Enomoto et al. 2020 H. amylolytica Yang et al. 2007 ["H. aidinensis"] H. hispanica Juez et al. 1986 H. japonica Takashina et al. 1991 H. marismortui Elazari-Volcani 1940 ex Oren et al. 1990 [H. quadrata, "H. californiae", "H. sinaiiensis"] H. argentinensis Ihara et al. 1997 [H. tradensis] H. sebkhae Barreteau et al. 2019

Unassigned Haloarcula

• "H. ajinwuensis"
• "H. algeriensis" Kharroub et al. 2005b
• "H. altuensis"
• "H. brevis" Ma et al. 2024
• H. halobia Ma et al. 2024
• H. halophila Ma et al. 2024
• H. litorea Ma et al. 2024
• "H. morrhuae" Torreblanca et al. 1986
• H. ordinaria Ma et al. 2024
• H. pelagica Ma et al. 2024
• H. rara Ma et al. 2024
• "H. regularis" Ma et al. 2024
• "H. sediminis" Ma et al. 2024
• "H. siamensis" Namwong et al. 2007

Ecology

Haloarcula species are found in neutral saline environments such as salt lakes, marine salterns, and saline soils. Like other members of the family Halobacteriaceae, Haloarcula requires at least 1.5 M NaCl for growth, but grow optimally in 2.0 to 4.5 M NaCl.^[1]

See also

• List of Archaea genera