Physiological and genomic features of Paraoceanicella profunda gen. nov., sp. nov., a novel piezophile isolated from deep seawater of the Mariana Trench

A novel piezophilic alphaproteobacterium, strain D4M1(T), was isolated from deep seawater of the Mariana Trench. 16S rRNA gene analysis showed that strain D4M1(T) was most closely related to Oceanicella actignis PRQ-67(T) (94.2%), Oceanibium sediminis O448(T) (94.2%), and Thioclava electrotropha ElOx9(T) (94.1%). Phylogenetic analyses based on both 16S rRNA gene and genome sequences showed that strain D4M1(T) formed an independent monophyletic branch paralleled with the genus Oceanicella in the family Rhodobacteraceae. Cells were Gram-stain-negative, aerobic short rods, and grew optimally at 37 degrees C, pH 6.5, and 3.0% (w/v) NaCl. Strain D4M1(T) was piezophilic with the optimum pressure of 10 MPa. The principal fatty acids were C-18:1 omega 7c/C-18:1 omega 6c and C-16:0, major respiratory quinone was ubiquinone-10, and predominant polar lipids were phosphatidylglycerol, phosphatidylethanolamine, and an unidentified aminophospholipid. The complete genome contained 5,468,583-bp with a G + C content of 70.2 mol% and contained 4,855 protein-coding genes and 78 RNA genes. Genomic analysis revealed abundant clues on bacterial high-pressure adaptation and piezophilic lifestyle. The combined evidence shows that strain D4M1(T) represents a novel species of a novel genus in the family Rhodobacteraceae, for which the name Paraoceanicella profunda gen. nov., sp. nov. is proposed (type strain D4M1(T) = MCCC 1K03820(T) = KCTC 72285(T)).