Pacificoceanicola niger sp. nov. and Pacificoceanicola algae sp. nov., isolated from the brown alga Saccharina japonica, with the reclassification of Tropicibacter oceani as Pacificoceanicola oceani comb. nov.

Two Gram-stain-negative, non-motile and oval-shaped bacterial strains, designated 2E107T and 2E233T, were isolated from the brown alga Saccharina japonica collected in Rongcheng, Weihai, China (122° 33' E 37° 15' N). The two strains shared 98.0% 16S rRNA gene sequence similarity. Both strains grew at 4-37 °C, with optimum growth at 35 °C, and tolerated 0.5-10% (w/v) NaCl. Strain 2E107T grew at pH 6.5-9.5, with optimum growth at pH 7.0 and 1.5% (w/v) NaCl, whereas strain 2E233T grew at pH 5.5-9.0, with optimum growth at pH 6.5 and 4% (w/v) NaCl. Strain 2E107T produced melanin, whereas strain 2E233T was non-pigmented. The genomic DNA G+C contents of strains 2E107T and 2E233T were 62.8 and 60.5 mol%, respectively. In both strains, summed feature 8 (C18 : 1  ω7c and/or C18 : 1  ω6c) was the predominant cellular fatty acid, and ubiquinone-10 was the sole respiratory quinone. The major polar lipids of strain 2E107T were phosphatidylcholine, phosphatidylglycerol, phosphatidylethanolamine and an unidentified lipid, whereas those of strain 2E233T were phosphatidylcholine, phosphatidylglycerol, phosphatidylethanolamine, an unidentified aminolipid and an unidentified lipid. The average nucleotide identity and average amino acid identity values between strain 2E107T and Pacificoceanicola onchidii XY-301T were 78.5 and 81.8%, respectively, whereas the corresponding values between strain 2E233T and P. onchidii XY-301T were 76.4 and 78.6%, respectively. On the basis of phylogenetic, phylogenomic, phenotypic and chemotaxonomic evidence, strains 2E107T and 2E233T are considered to represent two novel species of the genus Pacificoceanicola, for which the names Pacificoceanicola niger sp. nov. and Pacificoceanicola algae sp. nov. are proposed, respectively. The type strains are 2E107T (=MCCC 1H01529T=KCTC 8819T=SDUM152014T) and 2E233T (=MCCC 1H01530T=KCTC 8818T=SDUM152015T), respectively. Furthermore, on the basis of phylogenomic and comparative taxonomic evidence, Tropicibacter oceani Zhou et al. 2025 is proposed to be reclassified as Pacificoceanicola oceani comb. nov.