Octadecabacter jejudonensis sp. nov., isolated from the junction between the ocean and a freshwater spring and emended description of the genus Octadecabacter.

A Gram-stain-negative, non-spore-forming, non-flagellated, rod-shaped bacterial strain, SSK2-1(T), was isolated from the zone where the ocean and a freshwater spring meet at Jeju island, South Korea, and subjected to a polyphasic taxonomic study. Strain SSK2-1(T) grew optimally at 30 °C, at pH 7.0-8.0 and in the presence of 2.0% (w/v) NaCl. Neighbour-joining, maximum-likelihood and maximum-parsimony phylogenetic trees based on 16S rRNA gene sequences revealed that strain SSK2-1(T) clustered with the type strains of two Octadecabacter species, showing 96.5-96.8% 16S rRNA gene sequence similarity. Strain SSK2-1(T) and Octadecabacter arcticus DSM 13978(T) contained Q-10 as the predominant ubiquinone and C18 : 1ω7c as the common major fatty acid. The polar lipid profile of strain SSK2-1(T) was similar to that of O. arcticus DSM 13978(T) by having phosphatidylcholine, phosphatidylglycerol and one unidentified aminolipid as the major components. The DNA G+C content of strain SSK2-1(T) was 60.1 mol%. Differential phenotypic properties, particularly temperature range for growth, oxidase activity and nitrate reduction, together with phylogenetic distinctiveness, revealed that strain SSK2-1(T) is separate from recognized species of the genus Octadecabacter. On the basis of the data presented, strain SSK2-1(T) is considered to represent a novel species of the genus Octadecabacter, for which the name Octadecabacter jejudonensis sp. nov. is proposed. The type strain is SSK2-1(T) ( = KCTC 32535(T) = CECT 8397(T)).