Ulvibacterium marinum gen. nov., sp. nov., a novel marine bacterium of the family Flavobacteriaceae , isolated from a culture of the green alga Ulva prolifera Abstract A Gram-stain negative, aerobic, rod-shaped, and non-motile bacterium, designated strain CCMM003T, was isolated from a culture of the green alga Ulva prolifera. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain CCMM003T belongs to the family Flavobacteriaceae and exhibits a close relationship to Pseudozobellia thermophila DSM 19858T (92.5%). Optimal growth occurred in the presence of 4% (w/v) NaCl, at pH 7.0 and 30 °C. The polar lipids of strain CCMM003T consisted of phosphatidylethanolamine and six unidentified lipids. The predominant isoprenoid quinone was MK-6. The major fatty acids were iso-C15:0, iso-C15:1 G, iso-C17:0 3-OH and summed feature 3 (C16:1ω7c and/or iso-C15:0 2-OH). The DNA G + C content of strain CCMM003T calculated on the basis of the genome sequence was 41.2 mol% and the genome size was 5.9 Mbp. On the basis of data from this polyphasic study, strain CCMM003T is considered to represent a novel genus and species of the family Flavobacteriaceae, for which the name Ulvibacterium marinum gen. nov., sp. nov. is proposed. The type strain is CCMM003T (= MCCC 1K03244T =KCTC 52639T).