Two Gram-stain-negative, rod-shaped, facultatively anaerobic, iron-reducing bacterial strains, designated M2T and R106, were isolated from pelagic surface-sediment of the Ross Sea, Antarctica. The 16S rRNA gene sequence analysis revealed that strains M2T and R106 were affiliated to the genus Shewanellaand formed a distinct subline in a robust clade encompassing Shewanella vesiculosa, Shewanella livingstonensis, Shewanella arcticaand Shewanella frigidimarinawith a range of sequence similarities of 98.1-98.9 %. Overall genome relatedness indices indicated that M2T and R106 represented a single genomic species, which was clearly distinguishable from the phylogenetically close relatives with lower values of species delineation thresholds. Cells of M2T grew optimally at 10-15 °C and pH 6.5 in the presence of 3.0-4.0 % (w/v) sea salts. The polar lipids of M2T comprised phosphatidylglycerol, phosphatidylethanolamine, two unidentified aminophospholipids, an unidentified aminolipid and an unidentified phospholipid. Quinones were Q-7, Q-8, MK-7 and MMK-7. The major cellular fatty acids (>10 %) were C16 : 1ω7c and/or C16 : 1ω6c, C16 : 0 and C17 : 1ω8c. The DNA G+C content was 42.2 mol%. On the basis of the phenotypic, phylogenetic, genomic and chemotaxonomic features, we propose the name Shewanellapsychromarinicola sp. nov. with the type strain M2T (=KCCM 43257T =JCM 32090T) and the reclassification of S. arcticaas a later heterotypic synonym of S. frigidimarina.
Keywords: Antarctic; Shewanella psychromarinicola; new species; pelagic sediment; psychrophilic.