Roseobacter algicola sp. nov. and Sulfitobacter rhodophyticola sp. nov., Isolated from Marine Red Algae.

Two Gram-stain-negative, catalase- and oxidase-positive, non-motile strains, S98ᵀ and JB4-11ᵀ, were isolated from marine red algae. Strain S98ᵀ was a strictly aerobic, ovoid to short rod-shaped bacterium that grew at 15-30 °C, pH 7.0-9.0, and 1.0-4.0% (w/v) NaCl. In contrast, strain JB4-11ᵀ was a facultatively anaerobic, rod-shaped bacterium that grew at 20-30 °C, pH 7.0-10.0, and 1.0-7.0% (w/v) NaCl. Both strains contained phosphatidylglycerol, phosphatidylcholine, two unidentified aminolipids, and an unidentified phospholipid as major polar lipids, with JB4-11ᵀ additionally possessing diphosphatidylglycerol. The predominant fatty acids were summed feature 8 (C ω7c and/or C ω6c) and C, and both strains contained ubiquinone-10 as the sole isoprenoid quinone. The genomic DNA G + C content was 60.0% for S98ᵀ and 60.6% for JB4-11ᵀ. Strains S98ᵀ and JB4-11ᵀ shared 97.3% 16S rRNA gene sequence similarity and formed distinct lineages from other Roseobacter and Sulfitobacter species, with ≤ 98.1% similarity, in 16S rRNA gene-based phylogenetic trees. Genome-based phylogenetic analyses revealed that strains S98ᵀ and JB4-11ᵀ clustered with Roseobacter cerasinus AI77ᵀ and Sulfitobacter aestuariivivens TSTF-M16ᵀ within the genera Roseobacter and Sulfitobacter, respectively. Average nucleotide identity and digital DNA-DNA hybridization values with other Roseobacter and Sulfitobacter species were below 75.9% and 19.7%, respectively. Based on phenotypic, chemotaxonomic, and genomic characteristics, strains S98ᵀ and JB4-11ᵀ represent novel species of Roseobacter and Sulfitobacter, for which the names Roseobacter algicola sp. nov. and Sulfitobacter rhodophyticola sp. nov. are proposed. The type strains are S98ᵀ (= KACC 23419ᵀ = JCM 36648ᵀ) and JB4-11ᵀ (= KACC 23867ᵀ = JCM 36646ᵀ), respectively.