A Gram-staining-negative, yellow-pigmented, strictly aerobic bacterial strain motile by gliding, designated BS12(T), was isolated from a tidal flat at Boseong, Korea. Cells were moderately halotolerant, catalase- and oxidase-positive rods. Growth was observed at 5-40 °C (optimum, 25 °C), at pH 5.5-9.0 (optimum, pH 7.0-7.5) and in the presence of 1-11 % (w/v) NaCl (optimum, 2-4 %). The major cellular fatty acids were iso-C15 : 0, iso-C17 : 0 3-OH, iso-C17 : 1ω9c and anteiso-C15 : 0. The polar lipid pattern comprised phosphatidylethanolamine, four unidentified aminolipids and three unidentified lipids. The G+C content of the genomic DNA was 42.3 mol% and the only respiratory quinone was menaquinone 6. Phylogenetic inference based on 16S rRNA gene sequences showed that strain BS12(T) formed a tight phyletic lineage with members of the genus Gramella. Strain BS12(T) was most closely related to 'Gramella jeungdoensis' HMD3159 with sequence similarity of 97.5 %, but the DNA-DNA relatedness value between the two strains was only 22.1 ± 2.2 %. On the basis of phenotypic and molecular features, strain BS12(T) was shown to represent a novel species of the genus Gramella, for which the name Gramella aestuarii sp. nov. is proposed. The type strain is BS12(T) ( = KACC 16188(T) = JCM 17790(T)). An emended description of Gramella echinicola is also proposed.