A novel extremely halophilic archaeon was isolated from Ezzemoul sabkha, Algeria. The strain, designated 5.1(T), was neutrophilic, motile and Gram-negative. At least 15 % (w/v) NaCl was required for growth. The isolate grew at pH 6.5-9.0, with optimum growth at pH 7.0-7.5. Mg(2+) was required for growth. Polar lipids were C(20)C(20) derivatives of phosphatidylglycerol and phosphatidylglycerol phosphate methyl ester, and phosphatidylglycerol sulfate and sulfated diglycosyl diether. The genomic DNA G+C content of strain 5.1(T) was 61.9 mol% (T(m)). Phylogenetic analysis based on comparison of 16S rRNA gene sequences revealed that strain 5.1(T) clustered with Halorubrum species. The results of DNA-DNA hybridization and biochemical tests allowed genotypic and phenotypic differentiation of strain 5.1(T) from other Halorubrum species. The name Halorubrum ezzemoulense sp. nov. (type strain 5.1(T)=CECT 7099(T)=DSM 17463(T)) is proposed.