Genome taxonomy of the genus Neptuniibacter and proposal of Neptuniibacter victor sp. nov. isolated from sea cucumber larvae

A Gram-staining-negative, oxidase-positive, strictly aerobic rod-shaped bacterium, designated strain PT1(T), was isolated from the laboratory-reared larvae of the sea cucumber Apostichopus japonicus. A phylogenetic analysis based on the 16S rRNA gene nucleotide sequences revealed that PT1(T) was closely related to Neptuniibacter marinus ATR 1.1(T) (= CECT 8938(T) = DSM 100783(T)) and Neptuniibacter caesariensis MED92(T) (= CECT 7075(T) = CCUG 52065(T)) showing 98.2% and 98.1% sequence similarity, respectively. However, the average nucleotide identity (ANI) and in silico DNA-DNA hybridization (DDH) values among these three strains were 72.0%-74.8% and 18.3%-19.5% among related Neptuniibacter species, which were below 95% and 70%, respectively, confirming the novel status of PT1(T). The average amino acid identity (AAI) values of PT1(T) showing 74–77% among those strains indicated PT1(T) is a new species in the genus Neptuniibacter. Based on the genome-based taxonomic approach, Neptuniibacter victor sp. nov. is proposed for PT1(T). The type strain is PT1(T) (JCM 35563(T) = LMG 32868(T)).