An extremely halophilic archaeon, strain ETD6, was isolated from a marine solar saltern in Sfax, Tunisia. Analysis of the 16S rRNA gene sequence showed that the isolate was phylogenetically related to species of the genus Halorubrum among the family Halobacteriaceae, with a close relationship to Hrr. xinjiangense (99.77% of identity). However, value for DNA-DNA hybridization between strain ETD6 and Hrr.xinjiangense were about 24.5%. The G+C content of the genomic DNA was 65.1？mol% (T(m)). Strain ETD6 grew in 15–35% (w/v) NaCl. The temperature and pH ranges for growth were 20–55°C and 6–9, respectively. Optimal growth occurred at 25% NaCl, 37°C, and pH 7.4. The results of the DNA hybridization against Hrr. xinjiangense and physiological and biochemical tests allowed genotypic and phenotypic differentiation of strain ETD6 from other Hrr. species. Therefore, strain ETD6 represents a novel species of the genus Halorubrum, for which the name Hrr. sfaxense sp. nov. is proposed. The Genbank EMBL-EBI accession number is GU724599. 1. Introduction Extremely halophilic archaea belong into a single euryarchaeotal order (Halobacteriales) that inhabits various hypersaline environments (3–5？M) such as salt lakes, salt ponds, and marine salterns. Previous molecular ecology studies showed that archaeal halophiles dominate these ecosystems [1–3]. Halobacteriales contains a single family Halobacteriaceae with cultivated representatives in solar salterns. These organisms are known to promote crystal formation of halite [4]. Their cells act as seeds or nuclei to promote subsequent development of halite crystals [5]. The genus Halorubrum belongs to the family Halobacteriaceae, as first proposed by McGenity and Grant [6], and species of this genus are ubiquitous in hypersaline environments notably solar salterns. A recent study based on phylogenetic analysis of three ponds of the solar saltern of Sfax indicated that archaeal sequences were exclusively affiliated with the Halobacteriaceae: They were distributed among different genera of the Halobacteriaceae such as Haloquadratum, Halorubrum, and Halobacter [7]. Other studies assessing the diversity of halophilic Archaea in Korean salterns have shown that most sequences detected are grouped within the Halorubrum branch [8]. At the time of writing the genus Halorubrum [6, 9] contained 25 recognized species: Halorubrum aidingense [10], Halorubrum aquaticum [11], Halorubrum alkaliphilum [12], Halorubrum arcis [13], Halorubrum californiense [14], Halorubrum chaoviator [15], Halorubrum cibi [16], Halorubrum coriense [17, 18],
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