ScholarWorks@중앙대학교

초록

A Gram-stain-negative, strictly aerobic and motile rod, designated strain SyP6RT, was isolated from the freshwater alga Synura petersenii in Nakdong River, Republic of Korea, representing a niche expansion of Methylobacterium to the algae. Colonies were pink-coloured, convex and circular on Reasoner’s 2A agar. Phylogenetic analysis based on the 16S rRNA gene sequence indicated that strain SyP6RT formed a distinct phyletic lineage within the genus Methylobacterium, showing the highest similarity to Methylobacterium platani PMB02T (98.9%). Genomic G+C content was 69.6 mol%, and phylogenomic analysis supported its distinct phyletic lineage. The average nucleotide identity values (89.2–89.6%) and digital DNA–DNA hybridization values (36.3–38.2%) with the closely related taxa were clearly below the species delineation thresholds. Notably, strain SyP6RT possesses biosynthetic genes for B vitamins, including thiamine, riboflavin, pantothenate and folate, highlighting its potential ecological role as a vitamin-supplying symbiont. Strain SyP6RT was oxidase-positive and catalase-negative, growing optimally at 30 °C and pH 7.0 and 0.25% (w/v) NaCl. Strain SyP6RT possessed ubiquinone-10 as the sole respiratory quinone and C16:0, summed feature 5 (comprising C18:0 ante and/or C18:2 ω6,9c), C18:0, summed feature 3 (comprising C16:1 ω7c and/or C16:1 ω6c) and summed feature 8 (comprising C18:1 ω7c and/or C18:1 ω6c) as the major cellular fatty acids (>5%). The predominant polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and an unidentified aminolipid. Based on polyphasic evidence, strain SyP6RT represents a novel species of the genus Methylobacterium, for which the name Methylobacterium synurae sp. nov. is proposed. The type strain is SyP6RT (=KACC 19923T=JCM 33308T).

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