A Novel Paludibacterium Species Isolated from Human Blood

A novel facultatively anaerobic, Gram-negative, curved rod-shaped bacterium was isolated from blood cultures obtained from a patient with pyogenic spondylitis in Japan. The organism was additionally detected by 16S rRNA gene sequence analysis in a formalin-fixed, paraffin-embedded lumbar spine biopsy specimen from the same patient. The type strain, designated THUN1379ᵀ, is motile by means of a single polar flagellum and forms circular, white to translucent colonies on R2A agar and 5% sheep blood agar. The strain is oxidase-positive and catalase-negative and grows at temperatures ranging from 25 to 42 °C. Phylogenetic analysis based on the 16S rRNA gene sequence placed strain THUN1379ᵀ within the genus Paludibacterium (family Chromobacteriaceae), showing the highest sequence similarity to Paludibacterium purpuratum KJ031ᵀ (98.6%). Whole-genome sequencing revealed a genome size of approximately 3.6 Mb with a DNA G+C content of 61.3 mol%. Phylogenomic analysis based on whole-genome sequences supported the distinct taxonomic position of strain THUN1379ᵀ within the genus. The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between strain THUN1379ᵀ and Paludibacterium purpuratum KJ031ᵀ were 79.7% and 23.1%, respectively, which are well below the accepted thresholds for species delineation. On the basis of phenotypic, chemotaxonomic, and genomic characteristics, strain THUN1379ᵀ represents a novel species of the genus Paludibacterium, for which the name Paludibacterium flexuosum sp. nov. is proposed. The type strain is THUN1379ᵀ (=JCM 36560ᵀ = KCTC 8465ᵀ).