A Gram-negative, rod-shaped, strictly aerobic micro-organism, designated strain CL-GR60(T), was isolated from coastal seawater from the East Sea, Korea. A 16S rRNA gene sequence analysis revealed a clear affiliation with the family Hyphomicrobiaceae. Phylogenetic analyses showed that strain CL-GR60(T) formed a robust cluster with the species of the genus Devosia at sequence similarity levels of 91.1-93.1 %; no other species in the family Hyphomicrobiaceae shared more than 90 % sequence similarity with strain CL-GR60(T). The strain grew optimally in the presence of 3-4 % sea salts at 30-35 degrees C and pH 7. The major polar lipids were phosphatidylglycerol, diphosphatidylglycerol, two unidentified glycolipids, an unidentified phospholipid and an unidentified lipid. The strain contained C(18 : 1)omega7c (54.7 %), 11-methyl C(18 : 1)omega7c (19.3 %), C(18 : 0) (14.4 %) as the predominant fatty acids. Ubiquinone-10 was the major quinone. The DNA G+C content was 62.9 mol%. On the basis of physiological data, fatty acid composition and results of phylogenetic analysis of the 16S rRNA gene sequence, strain CL-GR60(T) represents a novel genus and species within the family Hyphomicrobiaceae, for which the name Cucumibacter marinus gen. nov., sp. nov. is proposed. The type strain of Cucumibacter marinus is CL-GR60(T) (=KCCM 90027(T) =DSM 18995(T)).