Description of Octadecabacter temperatus sp nov., isolated from the southern North Sea, emended descriptions of the genus Octadecabacter and its species and reclassification of Octadecabacter jejudonensis Park and Yoon 2014 as Pseudooctadecabacter jejudonensis gen. nov., comb. nov.

A heterotrophic, Gram-negative, aerobic bacterium, designated strain SB1(T), was isolated from surface water of the southern North Sea. Comparison of 16S rRNA gene sequences revealed that strain SB1(T) is affiliated to the genus Octadecabacter within the marine Roseobacter clade (family Rhodobacteraceae), with Octadecabacter antarcticus as the closest described species (98.2% sequence similarity to the type strain). DNA DNA hybridization indicated that SB1(T) represents a distinct species within this genus. On marine agar, strain SB1(T) formed beige, circular and convex colonies. Cells were irregular, motile rods. Growth occurred between 4 and 25 degrees C and was optimal at 20 degrees C, and at pH 7-9 (optimum pH 7.5-8.5) and NaCl concentrations between 1 and 6% (optimum 2-4%). The DNA G+C content of SB1(T) was 54.7 mol%. The fatty acids (>1%) comprised 10:0 3-OH, 12:1 3-OH, 16 :1 omega 7c, 16:0, 18:2 omega 7,12, 18 :1 omega 7c, 18:0 and 11-methyl 18 :1 omega 7c. The sole respiratory lipoquinone was ubiquinone Q-10 and the polar lipid pattern indicated the presence of the phospholipids phosphatidylglycerol and phosphatidylcholine, as well as unidentified aminolipid phospholipids PL1 and PL3 and lipids L1, L2 and L4. On the basis of phylogenetic and phenotypic differences, strain SB1(T) represents a novel species in the genus Octadecabacter, for which we propose the name Octadecabacter temperatus sp. nov. The type strain is SB1(T) (=DSM 26878(T)=LMG 27946(T)). Furthermore, our results suggest the reclassification of Octadecabacter jejudonensis as the type species of a new genus, Pseudooctadecabacter gen. nov., as Pseudooctadecabacter jejudonensis comb. nov. (type strain SSK2-1(T)=KCTC 32535(T)=CECT 8397(T)). Finally, emended descriptions of the genus Octadecabacter and its species Octadecabacter antarcticus and Octadecabacter arcticus are also provided.