Two　Gram-　stain-　negative,　motile,　non-　spore-　forming,　aerobic　or　facultative　anaerobic　and　short　rod-　shaped　bacterial　strains,　25B02-3T　and　BH-　R2-　4,　were　isolated　from　surface　seawater　collected　from　the　Bering　Sea　and　Chukchi　Sea,　respectively.　The　16S　rRNA　gene　sequences　of　the　two　strains　were　identical.　The　phylogenetic　analysis　of　the　16S　rRNA　gene　sequences　indicated　that　they　were　related　to　the　genus　Tistrella　and　shared　99.6　and　98.2%　sequence　similarity　with　T.　bauzanensis　BZ78T　and　T.　mobilis　IAM　14872T,　respectively.　Both　16S　rRNA　gene　and　genome　sequence-　based　phylogenetic　analyses　showed　that　the　two　strains　formed　a　monophyletic　clade　within　the　genus　Tistrella,　indicating　that　they　may　represent　a　novel　species.　The　digital　DNA-DNA　hybridization　(dDDH)　values　and　average　nucleotide　identities　(ANI)　between　the　two　strains　were　93　and　99%,　respectively,　indicating　that　they　are　different　strains.　The　dDDH　and　ANI　values　between　the　two　strains　and　the　type　strains　of　the　genus　Tistrella　were　22.4-58.3%　and　81.0-95.0%,　respectively.　These　data　clearly　demonstrated　that　the　two　strains　represent　a　separate　genomic　species　of　the　genus　Tistrella.　The　principal　fatty　acids　were　Sum　In　Feature　8　(C18　:　1　omega　7c　or　C18　:　1　omega　6c),　C19　:　0　cyclo　omega　8c,　Sum　In　Feature　2　(C12　:　0　aldehyde　or　unknown　10.928)　and　C16　:　0.　The　predominant　respiratory　quinone　was　Q-　10,　with　a　minor　Q-　9.　The　polar　lipids　included　phosphatidylethanolamine,　aminolipids　and　phospholipids.　The　genomic　DNA　G+C　contents　of　strains　25B02-　3T　and　BH-　R2-　4　were　67.3　mol%　and　67.4　mol%,　respectively.　On　the　basis　of　the　polyphasic　evidence　presented　in　this　study,　the　two　strains　represent　a　novel　species　within　the　genus　Tistrella,　for　which　the　name　Tistrella　arctica　sp.　nov.　is　proposed.　The　type　strain　is　25B02-　3T　(=MCCC　1A07333T=KCTC　8340T).