Siphonobacter curvatus sp. nov., isolated from a freshwater river

A novel orange-pigmented, Gram-stain-negative and strictly aerobic bacterium, designated strain HR-U^T, was isolated from a water sample of the Han River located in the Republic of Korea. Cells were catalase-positive and oxidase-positive, and non-motile curved rods without flagella. The strain grew at 5-35 °C (optimum 25 °C), pH 6-10 (optimum of 7-8) and 0-3 % (w/v) NaCl (optimum 0 %). Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain HR-U^T formed a tight phylogenic lineage with Siphonobacter aquaeclarae DSM 21668^T and 'Siphonobacter intestinalis' 63MJ-2. The 16S rRNA gene sequence comparison of strain HR-U^T and other reported type strains showed that it shared the highest sequence similarity to S. aquaeclarae DSM 21668^T (96.9 %) and 'S. intestinalis' 63MJ-2 (96.6 %), and had lower similarities than 87.0 % to other bacteria with validly published names. Average nucleotide identity and in silico DNA-DNA hybridization values between strain HR-U^T and the most closely related strain S. aquaeclarae were 71.7 and 18.4 %, respectively. The major respiratory quinone was menaquinone-7, and the dominant fatty acids (>5 %) consisted of C16 : 1ω5c, summed feature 3 (comprising C16 : 1ω7c and/or iso-C15 : 0 2-OH) and iso-C15 : 0. The polar lipids comprised phosphatidylethanolamine, four unidentified aminolipids and three unidentified lipids. The DNA G+C content was 47.9 mol%. Based on the genotypic, chemotaxonomic and phenotypic analyses, strain HR-U^T represents a novel species of the genus Siphonobacter, for which the name Siphonobacter curvatus sp. nov. is proposed. The type strain is HR-U^T (=KACC 19409^T=JCM 32267^T).