A bacterial strain, designated Iso4(T), was isolated from the East Sea of Korea and was subjected to a poly-phasic taxonomy study including phenotypic and chemotaxonomic characteristics as well as 16S rRNA gene sequence analysis. Cells of the strain were Gram-negative, motile, non-budding, non-stalked, and strictly aerobic. Strain Iso4(T) grew optimally at 20 degrees C in the presence of 1 approximately 2% (w/v) NaCl and at pH 6.9 approximately 7.6. The major respiratory quinone was Q-10 and the major cellular fatty acids were C(18:1) omega 7c (53.5%), C(17:1) omega 5c (11.7%), C(17:1) omega 6c (8.1%), C(16:0) (7.8%), C(17:0) (4.8%), C(15:0) (2.9%), and C(16:1) omega 5c (2.2%). The DNA G+C content of strain Iso4(T) was 56.2 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain Iso4(T) formed a monophyletic clade in the family Hyphomonadaceae, supported by high bootstrap value and was most closely related to the genus Hyphomonas (92 approximately 94%), a member of marine bacteria in the family. The phenotypic, genotypic, and chemotaxonomic evidences also suggest strain Iso4(T) represents a novel genus and species in the family Hyphomonadaceae, for which the name Henriciella gen. nov., sp. nov. is proposed. The type strain is Iso4(T) (=KCTC 12513(T) =DSM 19595(T) =JCM 15116(T)).