A novel Gram-stain-negative, moderately halophilic bacterium, designated strain 204(T), was isolated from a marine sediment sample in the Bohai Gulf, Yellow Sea, China. Cells of strain 204(T)are aerobic, motile, cocci or short rods with two lateral flagella. Growth was observed at 15-40 degrees C (optimum, 30 degrees C), pH 6.0-9.0 (optimum, 7.0-7.5) and in the presence of 1.0-18.0% (w/v) NaCl (optimum, 3.0-8.0%). Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain 204(T)belonged to the genusHalomonas, showing highest sequence similarity toHalomonas alimentariaYKJ-16(T)(98.08%), followed byHalomonas sediminicola(97.47%),Halomonas fontilapidosi(97.14%),Halomonas halodenitrificans(96.98%),Halomonas ventosae(96.92%), andHalomonas shengliensis(96.85%). The draft genome is 3.8 Mb in length, containing 3673 protein-coding genes, 62 tRNA genes and 10 rRNA genes, and DNA G+C content is 62.7 mol%. Strain 204(T)contains phosphatidylglycerol, phosphatidylethanolamine, and diphosphatidylglycerol as the main polar lipids, and the predominant respiratory quinone was ubiquinone Q-9. The major cellular fatty acids (> 5%) are C-18:1 omega 7c, C-16:1 omega 7c and/or C-16:1 omega 6c, C(16:0)and C(12:0)3-OH. Strain 204(T)was clearly distinguished from the closely related type strains through phylogenetic analysis, dDNA-DNA hybridization, fatty acid composition data and a range of physiological and biochemical characteristics comparisons. On the basis of the polyphasic analysis, strain 204(T)is considered to represent a novel species of the genus Halomonas, for which the name Halomonas marinisediminis sp. nov. is proposed. The type strain is 204(T)(= MCCC 1H00366(T) = KCTC 62957(T)).