Flagellimonas ulvae sp. nov. and Flagellimonas rhodophyticola sp. nov., isolated from marine algae

Two Gram-stain-negative, strictly aerobic, non-motile, rod-shaped bacteria, designated strains S174ᵀ and W118ᵀ, were isolated from the marine green alga <i>Ulva prolifera</i> and the marine red alga <i>Schizymenia dubyi</i>, respectively, collected in South Korea. Both strains exhibited catalase- and oxidase-positive activities and grew optimally at 25 °C, pH 8.0 and 2.0% (w/v) NaCl. The major fatty acids (>10%) in both strains were iso-C_15:1 G, iso-C_15:0 and iso-C_17:0 3-OH, with phosphatidylethanolamine as the major polar lipid and menaquinone-6 as the predominant respiratory quinone. The genomic DNA G+C contents, based on whole-genome sequences, were 39.1 mol% for both strains. Strains S174ᵀ and W118ᵀ shared 93.6% 16S rRNA gene sequence similarity, 72.7% average nucleotide identity (ANI) and 17.5% digital DNA-DNA hybridization (dDDH), supporting their classification as distinct species. Phylogenetic analyses based on 16S rRNA gene and genome sequences placed both strains in distinct lineages within the genus <i>Flagellimonas</i>. Strains S174ᵀ and W118ᵀ were most closely related to <i>Flagellimonas meridianipacifica</i> SW027ᵀ (97.2%) and <i>Flagellimonas onchidii</i> XY-359ᵀ (97.9%), respectively, and ANI and dDDH values with other type strains were below 84.6 and 28.2%, respectively, confirming their novelty. Based on phenotypic, chemotaxonomic and genomic features, strains S174ᵀ and W118ᵀ represent two novel species of the genus <i>Flagellimonas</i>, for which the names <i>Flagellimonas ulvae</i> sp. nov. (S174ᵀ=KACC 24029ᵀ=JCM 37803ᵀ) and <i>Flagellimonas rhodophyticola</i> sp. nov. (W118ᵀ=KACC 24030ᵀ=JCM 37802ᵀ) are proposed.