Marinomonas rhodophyticola sp. nov. and Marinomonas phaeophyticola sp. nov., isolated from marine algae.

Two Gram-stain-negative, facultatively aerobic, and motile rod bacteria, designated as strains KJ51-3T and 15G1-11T , were isolated from marine algae collected in the Republic of Korea. Both strains exhibited catalase- and oxidase-positive activities. Optimum growth conditions for strain KJ51-3T were observed at 30 °C and pH 6.0-8.0, with 1.0-7.0 % (w/v) NaCl, whereas strain 15G1-11T exhibited optimal growth at 30 °C, pH 7.0, and 1.0-5.0 % NaCl. Major fatty acids detected in both strains included C16 : 0 , C10 : 0 3-OH and summed features 3 (C16 : 1  ω 7 c and/or C16 : 1  ω 6 c ) and 8 (C18 : 1  ω 7 c and/or C18 : 1  ω 6 c ). As for polar lipids, strain KJ51-3T contained phosphatidylethanolamine (PE), phosphatidylglycerol (PG), diphosphatidylglycerol, and two unidentified phospholipids, whereas strain 15G1-11T had PE, PG, and an unidentified aminolipid. Ubiquinone-8 was the predominant respiratory quinone in both strains, with minor detection of ubiquinone-9 in strain KJ51-3T . The genomic DNA G+C contents were 44.0 mol% for strain KJ51-3T and 40.5 mol% for strain 15G1-11T . Phylogenetic analyses based on both 16S rRNA gene and genome sequences placed strains KJ51-3T and 15G1-11T into distinct lineages within the genus Marinomonas , most closely related to Marinomonas arctica 328T (98.6 %) and Marinomonas algicola SM1966T (98.3 %), respectively. Strains KJ51-3T and 15G1-11T exhibited a 94.6 % 16S rRNA gene sequence similarity and a 70.7 % average nucleotide identity (ANI), with ANI values of 91.9 and 79.3 % between them and M. arctica 328T and M. algicola SM1966T , respectively, indicating that they represent novel species. In summary, based on their phenotypic, chemotaxonomic, and phylogenetic properties, strains KJ51-3T and 15G1-11T are proposed to represent novel species within the genus Marinomonas , for which the names Marinomonas rhodophyticola sp. nov. (KJ51-3T =KACC 22756T =JCM 35591T ) and Marinomonas phaeophyticola sp. nov. (15G1-11T =KACC 22593T =JCM 35412T ) are respectively proposed.