Polaribacter ponticola sp. nov., isolated from seawater, reclassification of Polaribacter undariae as a later heterotypic synonym of Polaribacter sejongensis, and emended description of Polaribacter sejongensis Kim et al. 2013.

A Gram-stain-negative, yellow-pigmented, and strictly aerobic bacterium, designated as strain MSW5^T, was isolated from seawater of the Yellow Sea in South Korea. The cells were non-motile rods exhibiting oxidase- and catalase-positive activities. Growth was observed at 15-25 °C (optimum, 25 °C) and pH 5.0-9.0 (optimum, pH 7.0-8.0) and in the presence of 1.0-5.0% (w/v) NaCl (optimum, 2.0%). Menaquinone-6 was the sole respiratory quinone, and iso-C_15 : 0, summed feature 3 (C_16 : 1  ω7c and/or C_16 : 1  ω6c), iso-C_15 : 0 3-OH, and C_15 : 1  ω6c were the major cellular fatty acids. Major polar lipids included phosphatidylethanolamine, two unidentified aminolipids, and three unidentified lipids. Phylogenetic analyses based on 16S rRNA gene sequences and 92 concatenated core protein sequences revealed that strain MSW5^T formed a distinct lineage within the genus Polaribacter. The genome of strain MSW5^T was 3582 kb in size with a 29.1 mol% G+C content. Strain MSW5^T exhibited the highest similarity to Polaribacter atrinae WP25^T, with a 97.9% 16S rRNA gene sequence similarity. However, the average nucleotide identity and digital DNA-DNA hybridization values were 79.4 and 23.3%, respectively, indicating that strain MSW5^T represents a novel species. Based on its phenotypic, chemotaxonomic, and phylogenetic characteristics, strain MSW5^T is proposed to represent a novel species, with the name Polaribacter ponticola sp. nov. The type strain is MSW5^T (=KACC 22340^T=NBRC 116025^T). In addition, whole genome sequence comparisons and phenotypic features suggested that Polaribacter sejongensis and Polaribacter undariae belong to the same species, with P. undariae proposed as a later heterotypic synonym of P. sejongensis. An emended description of Polaribacter sejongensis is also proposed.