Ningiella algicola sp. nov. and Marinicella algicola sp. nov., proposal of Paralteromonas gen. Nov. and Neoalteromonas gen. Nov. with reclassification of Alteromonas species, and reclassification of Methylophaga aminisulfidivorans as a later heteroty

Two Gram-stain-negative, obligately aerobic, non-motile rod-shaped bacteria, designated strains W23^T and W31^T, exhibiting catalase- and oxidase-positive activities, were isolated from the phycosphere of a marine red alga. Strain W23ᵀ grew optimally at 25 °C, pH 8.0-9.0, and 3.0-4.0 % (w/v) NaCl, whereas strain W31^T grew optimally at 25-30 °C, pH 8.0, and 3.0-4.0 % NaCl. Ubiquinone-8 was the major respiratory quinone in both strains. Strain W23^T predominantly contained C_16:0, summed features 3 (C_16:1ω7c and/or C_16:1ω6c) and 8 (C_18:1ω7c and/or C_18:1ω6c), and C_12:0 as major fatty acids, with phosphatidylglycerol and phosphatidylethanolamine as main polar lipids. In contrast, strain W31^T exhibited isoC_15:0, summed feature 1 (isoC_15:1H and/or C_13:0 3-OH), C_12:0, and isoC_11:0, with diphosphatidylglycerol, phosphatidylethanolamine, and phosphatidylmonomethylethanolamine as dominant polar lipids. The genomic DNA G + C contents were 44.5 % for strain W23^T and 42.3 % for strain W31^T. Phylogenetic, genomic, and phenotypic analyses support the classification of strains W23ᵀ and W31ᵀ as novel species within the genera Ningiella and Marinicella, for which the names Ningiella algicola sp. nov. (W23^T = KACC 23126^T = JCM 35964^T) and Marinicella algicola sp. nov. (W31^T = KACC 23129^T = JCM 35965^T) are proposed. Genome-based phylogenomic analyses also supported the reclassification of Alteromonas lipolytica, Alteromonas alba, and Alteromonas oceani into the genus Marisediminitalea; Alteromonas sediminis into a new genus, Paralteromonas; and Alteromonas flava, Alteromonas facilis, and Alteromonas arenosi into another new genus, Neoalteromonas. Furthermore, Methylophaga aminisulfidivorans is reclassified as a later heterotypic synonym of Methylophaga thalassica.