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　degrees　C　(optimum　10-15　degrees　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　omega　6,9c　or　C-18:2　omega　6,9c/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)).