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 <i>Oceanobacter mangrovi</i> SM2-42^T (97.2%), followed by <i>Thalassolituus oleivorans</i> MIL-1^T (96.5%) and <i>Oceanobacter kriegii</i> 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 <i>Oceanobacter</i> 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 <i>Oceanobacter</i> and <i>Thalassolituus</i> 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 <i> ω6</i>,9<i>c</i> or C_18:2 <i> ω6</i>,9<i>c</i>/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 <i>Oceanobacter</i>, for which the name <i>Oceanobacter antarcticus</i> sp. nov. was proposed. The type strain was wDCs-4^T (=MCCC 1A20726^T=KCTC 8314^T).