Vibrio phycocola sp. nov. and Vibrio phycohabitans sp. nov., Isolated from the Phycosphere of Marine Algae

초록

Two Gram-stain-negative, facultatively aerobic, oxidase- and catalase-positive, motile (by means of a polar flagellum) rod-shaped bacterial strains, designated BS-M-Sm-2T and MA40-2T, were isolated from marine algae. Growth was optimal at pH 7.0–8.0 and 2.0–3.0% (w/v) NaCl, with temperature optima of 25°C for BS-M-Sm-2T and 25–30°C for MA40-2T. Ubiquinone-8 was the sole respiratory quinone. The major fatty acids common to both strains were C16:0, summed feature 3 (C16:1 ω7c and/or C16:1 ω6c), and summed feature 8 (C18:1 ω7c and/or C18:1 ω6c), while BS-M-Sm-2T additionally contained C12:0 and C14:0. The predominant polar lipids were phosphatidylethanolamine and phosphatidylglycerol, with diphosphatidylglycerol also detected in strain MA40-2T. The DNA G+C contents of strains BS-M-Sm-2T and MA40-2T were 44.2 and 39.8 mol%, respectively. The 16S rRNA gene sequence similarity, average nucleotide identity (ANI), and digital DNA-DNA hybridization (dDDH) values between the two strains were 93.8%, 71.4%, and 23.2%, respectively. Phylogenetic and phylogenomic analyses placed both strains within the genus Vibrio, forming distinct lineages. Comparisons with closely related Vibrio type strains yielded ANI and dDDH values below 91.6% and 44.3%, respectively, further supporting their classification as novel species. Genome analyses revealed genes potentially involved in algal symbiosis, including those for polysaccharide degradation and vitamin biosynthesis. Based on comprehensive genomic, phylogenetic, phenotypic, and chemotaxonomic evidence, strains BS-M-Sm-2T and MA40-2T represent two novel species, for which the names Vibrio phycocola sp. nov. (BS-M-Sm-2T =KACC 24066T =DSM 119941T) and Vibrio phycohabitans sp. nov. (MA40-2T =KACC 24064T = DSM 119942T) are proposed.

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