Octadecabacter algicola sp. nov. and Octadecabacter dasysiphoniae sp. nov., isolated from a marine red alga and emended description of the genus Octadecabacter

Abstract

Two Gram-stain-negative, strictly aerobic, catalase- and oxidase-positive and non-motile rod-shaped bacteria, strains D2-3T and G9-8T, were isolated from a marine red alga. Both strains contained ubiquinone-10 as the sole isoprenoid quinone. As the major cellular fatty acids (>5.0 %), D2-3T contained C16 : 0, 11-methyl-C18 : 1ω7c, summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c), and summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c), whereas G9-8T contained C16 : 0, 11-methyl-C18 : 1ω7c, C12 : 1 3-OH, and summed feature 8. The DNA G+C contents of D2-3T and G9-8T were 54.4 % and 56.0 %, respectively. As the major polar lipids, phosphatidylglycerol, diphosphatidylglycerol and unidentified phospholipid, aminolipid and lipid were identified from both strains, and phosphatidylcholine was additionally detected from G9-8T only. The 16S rRNA gene sequence similarity of D2-3T and G9-8T was 98.5 % and their digital DNA–DNA hybridization (DDH) value was 19.1 %. Phylogenetic analyses based on 16S rRNA gene and genome sequences revealed that D2-3T and G9-8T formed respectively distinct phylogenetic lineages within the genus Octadecabacter . D2-3T and G9-8T were most closely related to Octadecabacter ascidiaceicola RA1-3T and Octadecabacter antarcticus 307T, with 98.9 % and 98.5 % 16S rRNA gene sequence similarities, respectively, and digital DDH values between D2-3T and O. ascidiaceicola and between G9-8T and O. antarcticus were 18.3 % and 19.5 %, respectively. Phenotypic, chemotaxonomic and molecular features support the hypothesis that D2-3T and G9-8T represent two novel species of the genus Octadecabacter , for which the names Octadecabacter algicola sp. nov. and Octadecabacter dasysiphoniae sp. nov. are proposed. The type strains of O. algicola and O. dasysiphoniae are D2-3T (=KACC 22493T =JCM 34969T) and G9-8T (=KACC 22488T =JCM 34973T), respectively.