Methylobacterium synurae sp. nov., isolated from a freshwater alga Synura petersenii

A Gram-stain-negative, strictly aerobic and motile rod, designated strain SyP6R^T, 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 SyP6R^T formed a distinct phyletic lineage within the genus Methylobacterium, showing the highest similarity to Methylobacterium platani PMB02^T (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 SyP6R^T possesses biosynthetic genes for B vitamins, including thiamine, riboflavin, pantothenate and folate, highlighting its potential ecological role as a vitamin-supplying symbiont. Strain SyP6R^T was oxidase-positive and catalase-negative, growing optimally at 30 °C and pH 7.0 and 0.25% (w/v) NaCl. Strain SyP6R^T possessed ubiquinone-10 as the sole respiratory quinone and C_16:0, summed feature 5 (comprising C_18:0 ante and/or C_18:2 ω6,9c), C_18:0, summed feature 3 (comprising C_16:1 ω7c and/or C_16:1 ω6c) and summed feature 8 (comprising C_18:1 ω7c and/or C_18:1 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 SyP6R^T represents a novel species of the genus Methylobacterium, for which the name Methylobacterium synurae sp. nov. is proposed. The type strain is SyP6R^T (=KACC 19923^T=JCM 33308^T).