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A Gram-stain-negative, aerobic, orange-pigmented, rod-shaped and non-motile bacterium, designated strain A6B8T, was isolated from seawater of the Mariana Trench. The isolate grew at 4–50 6C (optimum 30–35 6C), at pH 6.5–8.0 (optimum pH 7.5) and with 0.5–4.0 % (w/v) NaCl (optimum 1.0–2.0%). Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain A6B8T was related most closely to the genus Muriicola and shared highest sequence similarity of 97.7 % with Muriicola jejuensis EM44T. Chemotaxonomic analysis showed menaquinone 6 (MK-6) was the predominant isoprenoid and iso-C15: 0, iso-C15: 1 G and iso-C17: 0 3-OH were the major cellular fatty acids. The polar lipid profile of strain A6B8 T included phosphatidylethanolamine, three unidentified aminolipids and four unidentified lipids. The genomic DNA G+C content was 47.1 mol%. The DNA–DNA relatedness value (23.3%) clearly demonstrated that strains A6B8T and M. jejuensis EM44T were representatives of two different species. Based on the phenotypic, phylogenetic and chemotaxonomic characterizations, A6B8T (5CGMCC 1.12606T5KCTC 32436T) is considered to be the type strain of a novel species of the genus Muriicola, for which the name Muriicola marianensis sp. nov. is proposed. The single-species genus Muriicola was first proposed by Kahng et al. (2010) with the description of Muriicola jejuensis. This genus was classified within the family Flavobacteriaceae, which was proposed by Reichenbach (1989) and the description later emended by Bernardet et al. (2002). Isolates of the family Flavobacteriaceae are short to moderately long rods, Gram-negative, non-spore-forming, non-motile or motile by gliding and aerobic. The majority of members of the family Flavobacteriaceae are pigmented by carotenoid or flexirubin pigments or both. Most species within the family Flavobacteriaceae have been isolated from various coastal marine habitats, such as tida