A novel Gram-positive, halotolerant, non-sporulating, non-motile, catalase-positive, oxidase-negative and aerobic bacterium, designated strain JSM 078085(T), was isolated from sea water collected from the South China Sea. Strain JSM 078085(T) exhibited a rod-coccus growth cycle and produced a yellow pigment. The strain was able to grow in the presence of 0-12% (w/v) NaCl and at pH 6.0-9.5 and 4-35 degrees C; optimum growth was observed at pH 7.0 and 25-30 degrees C in the absence of NaCl. The peptidoglycan type was A4alpha (L: -Lys-L: -Ala-L: -Glu). Cell-wall sugars contained galactose and glucose. Strain JSM 078085(T) contained menaquinone MK-9(H(2)) as the major respiratory quinone and diphosphatidylglycerol, phosphatidylglycerol and phosphatidylinositol as the major polar lipids. The major cellular fatty acids were anteiso-C(15:0), iso-C(15:0) and anteiso-C(17:0) and the DNA G + C content was 63.3 mol%. Phylogenetic analysis based on 16S rRNA gene sequence comparisons revealed that strain JSM 078085(T) should be assigned to the genus Arthrobacter, being most closely related to the type strain of Arthrobacter rhombi (sequence similarity 97.1%), and the two strains formed a distinct lineage in the phylogenetic tree. The level of DNA-DNA relatedness between strain JSM 078085(T) and the type strain of Arthrobacter rhombi was 10.6%. The combination of phylogenetic analysis, DNA-DNA relatedness, phenotypic characteristics and chemotaxonomic data supported the view that strain JSM 078085(T) represents a novel species of the genus Arthrobacter, for which the name Arthrobacter halodurans sp. nov. is proposed. The type strain is JSM 078085(T) (=DSM 21081(T)=KCTC 19430(T)).