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

A novel bacterial strain UR115^T belonging to the class <i>Alphaproteobacteria</i> 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 <i>Alphaproteobacteria</i>. 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 <i>Alphaproteobacteria</i>. 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 <i>ω</i>8<i>c</i>, C_{16 : 0} and summed feature 8 (C_{18 : 1} <i> ω</i>7<i>c</i> and/or C_{18 : 1} <i> ω</i>6<i>c</i>). 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 <i>Radicibacter daui</i> gen. nov., sp. nov., the novel family <i>Radicibacteraceae</i> fam. nov. and the novel order <i>Radicibacterales</i> ord. nov. The type strain is strain UR115^T (=KACC 23674^T=JCM 36738^T).