Haloferax larsenii

Haloferax larsenii is a gram-negative, aerobic, neutrophilic, extremely halophilic archaeon. It was named in honor of Professor Helge Larsen, who pioneered research on halophiles.[1]

Haloferax larsenii
Scientific classification
Domain:
Archaea
Phylum:
Euryarchaeota
Class:
Halobacteria
Order:
Halobacteriales
Family:
Halobacteriaceae
Genus:
Haloferax
Species:
H. larsenii
Binomial name
Haloferax larsenii
Xue-Wei Xu et al. 2007[1]

Discovery

Haloferax larsenii was isolated from a solar saltern in the Zhoushan archipelago, Zhejiang Province, China. The researchers who discovered this species isolated three strains of H. larsenii. When this species was discovered, the genus Haloferax comprised Haloferax volcanii, H. mediterranei, H. denitrificans, H. gibbonsii, H. alexandrinus, H. lucentense, and H. sulfurifontis.[1] Since this time, H. prahovense, H. elongans, and H. mucosum have been discovered, which totals to 11 species in the genus.[2]

Diversity

Like most species in Haloferax, H. larsenii was isolated from an extremely salty environment consisting of a mixture of mud and brine.[1]

Phylogenetic position

The species has been placed in a phylogeny:[3]

 
 

Haloferax elongans

 
 

Haloferax larsenii

 
 
 
 

Haloferax sulfurifontis

 
 
 

Haloferax mucosum

 
 
 

Haloferax prahovense

 
 
 
 

Haloferax gibbonsii

 
 

Haloferax lucentensis

 
 
 
 

Haloferax denitrificans

 
 
 

Haloferax volcanii

 
 
 

Haloferax alexandrinus

 
 
 
 
 
 
 
 

Characteristics

Cells of H. larsenii are extremely pleomorphic and irregularly shaped with a diameter of 0.8-1.5 µm. Motility of cells has been noted, but flagella have not been observed by electron microscopy. The major polar lipids are the C20C20 derivatives of phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, diglycosyl glycerol diether, and sulfated diglycosyl diether. The DNA G+C content of DNA of the ZJ206T strain is 62.2±0.8 mol% as determined by thermal denaturation.

When grown on complex agar medium, colonies appeared orange-red, smooth, circular, elevated, and 1–2 mm in diameter. Colonies can grow with NaCl concentrations of 1.0-4.8 M, with optimum growth between 2.2 and 3.4 M. However, saturated NaCl inhibits growth in liquid medium. The optimum pH for growth is 6.5-7.0 and the optimum temperature for growth is 42-45oC. Anaerobic growth occurs on nitrate with the production of gas; nitrate is reduced to nitrite.

Glucose, glycerol, mannose, starch, maltose, sucrose, glutamate, alanine, ornithine, fumarate, malate, pyruvate, succinate, and lactate substrates support growth. Growth is not sustained on arabinose, lactose, mannitol, rhamnose, sorbitol, galactose, ribose, xylose, arginine, lysine, aspartate, glycine, acetate, propionate, and citrate.

Sensitivity to novobiocin, bacitracin, anisomycin, aphidicolin, and rifampicin have been observed. However, no sensitivity has been shown to ampicillin, penicillin, chloramphenicol, erythromycin, neomycin, nalidixic acid, nystatin, tetracycline, streptomycin, or kanamycin.

Furthermore, H. larsenii was shown to form indole, hydrolyze gelatin, starch, and Tweens 40 and 80; produce acid from glycerol, maltose, glucose, fructose, and sucrose; and form H2S from thiosulfate.[1]

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References
  1. Xu, Xue-Wei; et al. (2007). "Haloferax larsenii sp. nov., an extremely halophilic archaeon from a solar saltern". International Journal of Systematic and Evolutionary Microbiology. 57 (4): 717–720. doi:10.1099/ijs.0.64573-0. PMID 17392193. Archived from the original on 2014-11-20.
  2. Allen, Michelle A.; et al. (2008). "Haloferax elongans sp. nov. and Haloferax mucosum sp. nov., isolated from microbial mats from Hamelin Pool, Shark Bay, Australia". International Journal of Systematic and Evolutionary Microbiology. 58 (4): 798–802. doi:10.1099/ijs.0.65360-0. PMID 18398172.
  3. Tekin, Ebru; Ateş, Mustafa; Kahraman, Özge (2012). "Poly-3-hydroxybutyrate-producing extreme halophilic archaeon: Haloferax sp. MA10 isolated from Çamaltı Saltern, İzmir". Turk J Biol. 36: 303–312.
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