| Abstract |
Two Gram-stain-negative, facultatively aerobic, non-motile, catalase- and oxidase-positive, rod-shaped bacteria, designated strains DGS2-2T (orange-pigmented) and DGS5-3T (yellow-pigmented), were isolated from marine red algae collected in Korea. Strain DGS2-2T grew at 20-40°C, pH 6.0-10.0, and in 1.0-6.0% (w/v) NaCl, while DGS5-3T grew at 15-40°C, pH 6.0-10.0, and in 2.0-6.0% NaCl. Ubiquinone-10 was the sole respiratory quinone. The G+C contents were 62.5% for DGS2-2T and 57.5% for DGS5-3T. Both strains contained summed feature 8 (C18:1ω7c and/or C18:1ω6c) and C16:0 as major fatty acids, and phosphatidylcholine, sphingoglycolipid, phosphatidylethanolamine, phosphatidylglycerol, and diphosphatidylglycerol as major polar lipids. The 16S rRNA gene similarity (97.3%), average nucleotide identity (ANI, 72.0%), and digital DNA-DNA hybridization (dDDH, 18.4%) values between the two strains were below the species delineation thresholds. Phylogenetic and phylogenomic analyses based on 16S rRNA gene and whole-genome sequences placed both strains in distinct lineages within the genus Qipengyuania. ANI and dDDH values between each strain and Qipengyuania type strains were below 74.5% and 19.5%, respectively, supporting their designation as novel species. Genomic analyses identified putative genes associated with potential algal symbiotic traits, including the biosynthesis of vitamins, siderophores, and hormone-like compounds. Carotenoid biosynthetic genes were also identified, and LC/MS confirmed astaxanthin (DGS2-2T) and nostoxanthin (DGS5-3T) production. Based on genomic, phylogenetic, phenotypic, and chemotaxonomic evidence, strains DGS2-2T and DGS5-3T represent two novel species of Qipengyuania, for which the names Qipengyuania algicola sp. nov. (DGS2-2T =KACC 23855T =JCM 37496T) and Qipengyuania rhodophyticola sp. nov. (DGS5-3T =KACC 23854T =JCM 37497T) are proposed.
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