A novel halophilic archaeon, NG4(T), was isolated from Jilantai salt lake in Inner Mongolia, China. The taxonomy of strain NG4(T) was studied by polyphasic methods. Strain NG4(T) grew at pH 5.5-8.5 and at a temperature of 22-55 degrees C. It was chemo-organotrophic, aerobic and required concentrations of 2.7-5.2 M NaCl and 0.05-0.3 M Mg(2+) for growth. Cells were Gram-negative, slender rods. Colonies on agar plates containing 25 % (w/v) total salts were red, elevated and round. According to 16S rRNA gene sequence similarity, strain NG4(T) was phylogenetically related to Halobacterium salinarum DSM 3754(T) (98.2 %) and Halobacterium noricense A1(T) (97.3 %). The DNA G+C content was 64.2 mol%. DNA-DNA relatedness values with Hbt. salinarum DSM 3754(T) and Hbt. noricense A1(T) were 47 and 35 %, respectively. The polar lipids of strain NG4(T) consisted of phosphatidylglycerol, methylated phosphatidylglycerol phosphate, phosphatidylglycerol sulfate, triglycosyl diether, sulfated triglycosyl diether and sulfated tetraglycosyl diether. It was concluded that strain NG4(T) represents a novel species of the genus Halobacterium, for which the name Halobacterium jilantaiense sp. nov. is proposed. The type strain is NG4(T) (=CGMCC 1.5337(T)=JCM 13558(T)).