Oceanobacter antarcticus sp. nov., isolated from surface seawater of the Weddell Sea in Antarctica

The poles of the Earth harbour many novel micro-organisms that have not yet been isolated and identified. Here, a Gram-stain-negative, motile, aerobic and rod-shaped bacterial strain, designated as wDCs-4 T , was isolated from surface seawater collected from the Weddell Sea in Antarctica. It grows at 4–40 °C (optimum 10–15 °C), pH 4–8 (optimum 7) and in the presence of 0–4% NaCl (w/v, optimum 0.5–1%). The complete 16S rRNA gene of strain wDCs-4 T had maximum sequence identity with Oceanobacter mangrovi SM2-42 T (97.2%), followed by Thalassolituus oleivorans MIL-1 T (96.5%) and Oceanobacter kriegii 197 T (96.2%). Phylogenetic analyses based on the 16S rRNA gene and genome sequences showed that strain wDCs-4 T was closely clustered with the members of the genus Oceanobacter and formed an independent clade, which could be considered a monophyletic taxon. The average nucleotide identity values between strain wDCs-4 T and the members of the genera Oceanobacter and Thalassolituus were 77.7–78.1 and 77.4–80.5%, respectively. The corresponding digital DNA‒DNA hybridization values are 19.5–20.1 and 20.5–22.4%, respectively. The major fatty acids (>5%) of strain wDCs-4 T comprised summed feature 5 (C 18:0 ante/C 18:2 ω6 ,9 c or C 18:2 ω6 ,9 c /C 18:0 ante) and C 16:0 . The predominant respiratory was Q-8. The polar lipid profile consisted of phosphatidylethanolamine, phosphatidylglycerol, aminolipids and unknown polar lipids. The draft genome size was 4.58 Mbp, with a DNA G+C content of 53.4 mol%. On the basis of polyphasic analyses, strain wDCs-4 T represented a novel species in the genus Oceanobacter , for which the name Oceanobacter antarcticus sp. nov. was proposed. The type strain was wDCs-4 T (=MCCC 1A20726 T =KCTC 8314 T ).