A novel extremely halophilic strain, AJ2(T), was isolated from Ayakekum salt lake located in the Altun Mountain National Nature Reserve in Xinjiang, China. This isolate was neutrophilic, motile and grew in a wide range of MgCl(2) concentrations (0.005-1.0 M). The major polar lipids of the isolate were C(20)C(20) and C(20)C(25) derivatives of phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester and phosphatidylglycerol sulfate. A comprehensive 16S rRNA gene sequence analysis revealed that the isolate shared 96.6-97.7 % sequence identity with Natrinema species. The isolate, however, could be genetically differentiated from these species by DNA-DNA hybridization analysis and on the basis of its physiological properties. On the basis of the polyphasic evidence, strain AJ2(T) (= AS 1.3731(T) = JCM 12890(T)) represents the type strain of a novel species, for which the name Natrinema altunense sp. nov. is proposed.