Radicibacter daui, gen. nov., sp. nov., isolated from tomato rhizosphere soil and proposal of Radicibacteraceae fam. nov. and Radicibacterales ord. nov.

Abstract

A novel bacterial strain UR115^T belonging to the class Alphaproteobacteria was isolated from tomato rhizosphere soil. Strain UR115^T was Gram-stain-negative, motile, facultative anaerobic, catalase positive, oxidase positive and rod shaped. Strain UR115^T showed growth at 15-37 °C, pH 5.5-9.5 and up to 4.0% NaCl. Strain UR115^T exhibited 16S rRNA gene sequence similarities of <90.40% with members of the class Alphaproteobacteria. Based on the phylogenetic analysis inferred from both 16S rRNA gene and whole-genome sequences, strain UR115^T formed a separate and distinct clade, leading to its classification as a member of a novel order within the class Alphaproteobacteria. The genome size and G+C content of strain UR115^T were 5,059,753 bp and 63.9%, respectively. Average amino acid identity values between strain UR115ᵀ and reference genomes ranged from 47.85% to 59.96%, and pairwise Percentage of Conserved Protein values ranged from 4.12% to 46.63%. The major cellular fatty acids of strain UR115^T were C_19 : 0 cyclo ω8c, C_16 : 0 and summed feature 8 (C_18 : 1  ω7c and/or C_18 : 1  ω6c). The polar lipids of strain UR115^T were phosphatidylethanolamine, phosphatidylglycerol, unidentified aminophospholipid, two unidentified aminolipids and two unidentified lipids. The predominant quinone was ubiquinone-10. Based on its distinct phylogenetic position, unique genomic characteristics and chemotaxonomic profiles, we proposed the novel species Radicibacter daui gen. nov., sp. nov., the novel family Radicibacteraceae fam. nov. and the novel order Radicibacterales ord. nov. The type strain is strain UR115^T (=KACC 23674^T=JCM 36738^T).