Poseidonibacter ostreae sp. nov., Isolated from the Gut of Ostrea from the Seomjin River

Three Gram-negative strains, SJOD-M-6(T), SJOD-M-5, and SJOD-M-33, were isolated from Ostrea denselamellosa. These strains are oxidase- and catalase-positive coccoids that thrive aerobically. The three strains shared 100.0% 16S rRNA gene sequence similarity and showed average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values of 99.7-99.8% and 93.8-96.8%, suggesting that they belonged to the same species. Phylogenetic analysis based on the 16S rRNA gene revealed that all three isolates belong to the genus Poseidonibacter. Their closest neighbors were Poseidonibacter parvus LPB0137(T) (98.8%), Poseidonibacter antarcticus SM1702(T) (98.7%), and Poseidonibacter lekithochrous LFT 1.7(T) (95.5%). However, the ANI and dDDH values between SJOD-M-6(T) (the representative strain of the novel species) and its closest phylogenetic relatives fell well below the established cut-off values of <95% (ANI) and <70% (dDDH) for species delineation. Furthermore, several phenotypic traits distinguish the novel strains from their closest relatives. Based on the combined genotypic and phenotypic data, strains SJOD-M-6(T), SJOD-M-5, and SJOD-M-33 are classified as novel species within the genus Poseidonibacter. We propose the name Poseidonibacter ostreae sp. nov. for this novel species, with the type strain being SJOD-M-6(T )(=KCTC 72758(T) = NBRC 114334(T) = FBCC-B685).

Automated summary

Three novel Gram-negative strains, SJOD-M-6(T), SJOD-M-5, and SJOD-M-33, isolated from Ostrea denselamellosa, belong to the same species within the genus Poseidonibacter. They show significant genetic and phenotypic differences from their closest relatives, suggesting the need for a new species designation.