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.

Abstract

A heterotrophic, Gram-negative, aerobic bacterium, designated strain SB1T, was isolated from surface water of the southern North Sea. Comparison of 16S rRNA gene sequences revealed that strain SB1T 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 SB1T represents a distinct species within this genus. On marine agar, strain SB1T formed beige, circular and convex colonies. Cells were irregular, motile rods. Growth occurred between 4 and 25 °C and was optimal at 20 °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 SB1T was 54.7 mol%. The fatty acids (>1 %) comprised 10 : 0 3-OH, 12 : 1 3-OH, 16 : 1ω7c, 16 : 0, 18 : 2ω7,12, 18 : 1ω7c, 18 : 0 and 11-methyl 18 : 1ω7c. 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 AL1, phospholipids PL1 and PL3 and lipids L1, L2 and L4. On the basis of phylogenetic and phenotypic differences, strain SB1T represents a novel species in the genus Octadecabacter, for which we propose the name Octadecabacter temperatus sp. nov. The type strain is SB1T ( = DSM 26878T = LMG 27946T). 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 SSK2-1T = KCTC 32535T = CECT 8397T). Finally, emended descriptions of the genus Octadecabacter and its species Octadecabacter antarcticus and Octadecabacter arcticus are also provided.