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 WS11^T, was isolated from a deep-sea sediment sample collected from the New Britain Trench. The full-length 16S rRNA gene of strain WS11^T had the highest sequence similarity of 97.6 % to Rhizobium subbaraonis JC85^T, followed by Mycoplana ramosa DSM 7292^T (96.9 %) and Rhizobium azooxidifex Po 20/26^T (96.8 %). Phylogenetic analysis of concatenated 16S rRNA, atpD and recA gene sequences showed that strain WS11^T was deeply separated from the species within the family Rhizobiaceae. Phylogenomic analysis based on the whole-genome protein sequences showed that strain WS11^T formed an independent monophyletic branch in the family Rhizobiaceae, paralleled with the species in the families Brucellaceae 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 WS11^T was piezotolerant, growing optimally at 0.1 MPa (range 0.1-70 MPa). The main fatty acid was summed feature 8 (C_{18 : 1} ω7c/C_{18 : 1} ω 6c). 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 WS11^T 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 WS11^T=MCCC 1K03498^T=KCTC 62439^T).

Keywords: Georhizobium profundi; Rhizobiaceae; piezotolerant.