A gram-staining negative, non-motile, aerobic chemoheterotrophic, ovoid or short rod-shaped bacterium, designated as J89(T), was isolated from a seawater sample collected from the coast of Yellow Sea in Qingdao, China. The strain grew at salinities of 1.0-6.0% (w/v) NaCl (optimum, 3.0%). Growth occurred at pH 6.0-9.0 (optimum, pH 7.0) and at 10-35 degrees C (optimum, 25-30 degrees C). The genomic DNA G+C content was determined to be 59.3 mol%. Q-8 was detected as the respiratory quinone. The major fatty acids (>10%) were summed feature 3 (C-16:1 omega 7c and/or C-16:1 omega 6c), summed feature 8 (C-18:1 omega 7c and/or C-18:1 omega 6c), and C-16:0. The polar lipids consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine, two unidentified phospholipids, and an unidentified polar lipid. Comparison of the 16S rRNA gene sequence indicated that the strain was most closely related (<91%) to members of the order Chromatiales in the class Gammaproteobacteria. Phylogenetic analyses showed that this strain represented a distinct phylogenetic lineage in the order Chromatiales and could not be assigned to any of the defined families in the order. On the basis of low sequence similarities and differential characteristics of strain J89(T) from the genera of neighboring families, the strain is proposed to be a representative of a novel genus Aquichromatium gen. nov. A new family Aquichromatiaceae with the type genus Aquichromatium is proposed. Strain J89(T) (=MCCC 1K03281T=CMRC C2017206T) is the type strain of the type species Aquichromatium aeriopus sp. nov.