Roseibium algicola sp. nov. and Roseibium porphyridii sp. nov., isolated from marine red algae.

Two Gram-stain-negative, strictly aerobic rods, designated as RMAR6-6T and KMA01T, exhibiting catalase- and oxidase-positive activities, were isolated from marine red algae in the Republic of Korea. Cells of strain RMAR6-6T exhibited flagellar motility, while those of strain KMA01T were non-motile. Strain RMAR6-6T exhibited optimal growth at 30-35°C and pH 7.0-8.0 with 4.0-6.0 % (w/v) NaCl, while strain KMA01T grew optimally at 30-35 °C, pH 7.0-8.0 and 2.0-5.0% NaCl. Both strains shared common major respiratory isoprenoid quinone (ubiquinone-10), cellular fatty acids (C18 : 0, C18: 1  ω7c 11-methyl, C20 : 1  ω7c and summed feature 8) and polar lipids (phosphatidylglycerol, phosphatidylmonomethylethanolamine, diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine and sulphoquinovosyldiacylglycerol). The genomic DNA G+C contents were 59.0 and 55.0 mol% for strains RMAR6-6T and KMA01T, respectively. With 98.5 % 16S rRNA gene similarity, 75.2 % average nucleotide identity (ANI) and 19.8 % digital DNA-DNA hybridization (dDDH) values, strains RMAR6-6T and KMA01T were identified as representing distinct species. Phylogenetic analyses based on both 16S rRNA gene and genome sequences revealed that strains RMAR6-6T and KMA01T formed distinct phylogenic lineages within the genus Roseibium, most closely related to Roseibium aggregatum IAM 12614T and Roseibium album CECT 5094T, respectively. The ANI and dDDH values between strain RMAR6-6T and R. aggregatum IAM 12614T were 87.5 and 33.3 %, respectively. Similarly, the values between KMA01T and R. album CECT 5094T were 74.2 % (ANI) and 19.3 % (dDDH). Based on phenotypic, chemotaxonomic and molecular characteristics, strains RMAR6-6T and KMA01T represent two novel species of the genus Roseibium, for which the names R. algicola sp. nov. (RMAR6-6T=KACC 22482T=JCM 34977T) and R. porphyridii sp. nov. (KMA01T=KACC 22479T=JCM 34597T) are proposed, respectively.