Georhizobium profundi gen. Nov., sp. nov., a piezotolerant bacterium isolated from a deep-sea sediment sample of the New Britain Trench

Abstract

A novel alphaproteobacterium, strain WS11T, was isolated from a deep-sea sediment sample collected from the New Britain Trench. The full-length 16S rRNA gene of strain WS11T had the highest sequence similarity of 97.6 % to Rhizobium subbaraonis JC85T, followed by Mycoplana ramosa DSM 7292T (96.9%) and Rhizobium azooxidifex Po 20/26T (96.8%). Phylogenetic analysis of concatenated 16S rRNA, atpD and recA gene sequences showed that strain WS11T was deeply separated from the species within the family Rhizobiaceae. Phylogenomic analysis based on the whole-genome protein sequences showed that strain WS11T formed an independent monophyletic branch in the family Rhizobiaceae, paralleled with the species in the families Bru-cellaceae and Phyllobacteriaceae within the order Rhizobiales. Cells were Gram-stain-negative, oxidase-and catalase-positive, and aerobic short rods (1.5–2.4×0.9–1.0 µm). Growth was observed at salinities ranging from 0 to 5% (optimum, 1 %), from pH 6.5 to 9 (optimum, pH 7) and at temperatures between 20 and 30 °C (optimum, 28 °C). Strain WS11T was piezotolerant, growing optimally at 0.1 MPa (range 0.1–70 MPa). The main fatty acid was summed feature 8 (C18:1 ω7c/C18:1 ω6c). The sole respiratory quinone was ubiquinone-10 (Q-10). The predominant polar lipids were phosphatidylcholine, two unidentified aminophospholipids and an unidentified phospholipid. The genome size was about 4.36 Mbp and the G+C content was 62.3 mol%. The combined genotypic and phenotypic data show that strain WS11T represents a novel species of a novel genus in the family Rhizobiaceae, for which the name Georhizobium profundi gen. nov., sp. nov. is proposed (type strain WS11T=MCCC 1K03498T=KCTC 62439T).