Siphonobacter curvatus sp nov., isolated from a freshwater river

Abstract

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 degrees C (optimum 25 degrees 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 C-16 : 1 omega 5c, summed feature 3 (comprising C-16 : 1 omega 7c and/or iso-C-15( : 0) 2-OH) and iso-C-15( : 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)).