Shimia rhodophyticola sp. nov., Neomarinovum algicola gen. nov., sp. nov., and Phycorhabdus gracilariae gen. nov., sp. nov., isolated from marine algae, and the taxonomic revision of nineteen taxa within the family Roseobacteraceae

Three bacterial strains, W99T, S113T, and S268T, were isolated from marine algae and subjected to polyphasic taxonomic characterization. Phylogenetic and phylogenomic analyses placed W99T within the genus Shimia, whereas S113T and S268T formed two distinct genus-level lineages within the family Roseobacteraceae. The three isolates were Gram-stain-negative, non-motile, and obligately aerobic, with optimum growth at 25, 25, and 30°C, respectively, and at 2.0% (w/v) NaCl. Ubiquinone-10 was the sole respiratory quinone in all three strains. The major fatty acids were 11-methyl C18:1 ω7c and summed feature 8 (C18:1 ω7c and/or C18:1 ω6c) in strain W99T; C16:0 and summed feature 8 in strain S113T; and 11-methyl C18:1 ω7c, cyclo-C19:0 ω8c, and summed feature 8 in strain S268T. The major polar lipids were phosphatidylglycerol and phosphatidylcholine, with diphosphatidylglycerol additionally detected in strain S268T. Polyphasic taxonomic analyses demonstrated that strain W99T represents a novel species of the genus Shimia, for which the name Shimia rhodophyticola sp. nov. is proposed (W99T = KACC 24154T = JCM 38196T), whereas strains S113T and S268T represent two novel genera and species, Neomarinovum algicola gen. nov., sp. nov. (S113T = KACC 23417T = JCM 38210T) and Phycorhabdus gracilariae gen. nov., sp. nov. (S268T = KACC 24156T = JCM 38211T), respectively. In addition, comprehensive phylogenomic and genome-based relatedness analyses support the taxonomic revision of nineteen taxa within the family Roseobacteraceae, providing a revised genome-based taxonomic framework that better reflects the evolutionary relationships within the family.