Shewanella psychromarinicola sp. nov., a psychrophilic bacterium isolated from pelagic sediment of the Ross Sea (Antarctica), and reclassification of Shewanella arctica Kim et al. 2012 as a later heterotypic synonym of Shewanella frigidimarina Bowman et al. 1997

Abstract

Two Gram-stain-negative, rod-shaped, facultatively anaerobic, iron-reducing bacterial strains, designated M2(T) and R106, were isolated from pelagic surface-sediment of the Ross Sea, Antarctica. The 16S rRNA gene sequence analysis revealed that strains M2(T) and R106 were affiliated to the genus Shewanella and formed a distinct subline in a robust Glade encompassing Shewanella vesiculosa, Shewanella livingstonensis, Shewanella arctica and Shewanella frigidimarina with a range of sequence similarities of 98.1-98.9 %. Overall genome relatedness indices indicated that M2(T) 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 M2(T) grew optimally at 10-15 degrees C and pH 6.5 in the presence of 3.0-4.0 % (w/v) sea salts. The polar lipids of M2(T) 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 C-16:1 omega 7c and/or C-16:1 omega 6c, C-16:0 and C-17:1 omega 8c. The DNA G+C content was 42.2 mol%. On the basis of the phenotypic, phylogenetic, genomic and chemotaxonomic features, we propose the name Shewanella psychromarinicola sp. nov. with the type strain M2(T) (=KCCM 43257(T) =JCM 32090(T)) and the reclassification of S. arctica as a later heterotypic synonym of S. frigidimarina.