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

Two Gram-stain-negative, strictly aerobic rods, designated as RMAR6-6^T and KMA01^T, exhibiting catalase- and oxidase-positive activities, were isolated from marine red algae in the Republic of Korea. Cells of strain RMAR6-6^T exhibited flagellar motility, while those of strain KMA01^T were non-motile. Strain RMAR6-6^T exhibited optimal growth at 30-35°C and pH 7.0-8.0 with 4.0-6.0 % (w/v) NaCl, while strain KMA01^T 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 (C_18 : 0, C_18: 1 ω7c 11-methyl, C_20 : 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 RMAR6-6^T and KMA01^T, respectively. With 98.5 % 16S rRNA gene similarity, 75.2 % average nucleotide identity (ANI) and 19.8 % digital DNA-DNA hybridization (dDDH) values, strains RMAR6-6^T and KMA01^T were identified as representing distinct species. Phylogenetic analyses based on both 16S rRNA gene and genome sequences revealed that strains RMAR6-6^T and KMA01^T formed distinct phylogenic lineages within the genus Roseibium, most closely related to Roseibium aggregatum IAM 12614^T and Roseibium album CECT 5094^T, respectively. The ANI and dDDH values between strain RMAR6-6^T and R. aggregatum IAM 12614^T were 87.5 and 33.3 %, respectively. Similarly, the values between KMA01^T and R. album CECT 5094^T were 74.2 % (ANI) and 19.3 % (dDDH). Based on phenotypic, chemotaxonomic and molecular characteristics, strains RMAR6-6^T and KMA01^T represent two novel species of the genus Roseibium, for which the names R. algicola sp. nov. (RMAR6-6^T=KACC 22482^T=JCM 34977^T) and R. porphyridii sp. nov. (KMA01^T=KACC 22479^T=JCM 34597^T) are proposed, respectively.