Ciceribacter sichuanensis sp. nov., a plant growth promoting rhizobacterium isolated from root nodules of soybean in Sichuan, China

The fast-growing rhizobia-like strains S101^T and S153, isolated from root nodules of soybean (Glycine max) in Sichuan, People’s Republic of China, underwent characterization using a polyphasic taxonomy approach. The strains exhibited growth at 20–40 °C (optimum, 28 °C), pH 4.0–10.0 (optimum, pH 7.0) and up to 2.0% (w/v) NaCl (optimum, 0.01%) on Yeast Mannitol Agar plates. The 16S rRNA gene of strain S101^T showed 98.4% sequence similarity to the closest type strain, Ciceribacter daejeonense L61^T. Major cellular fatty acids in strain S101^T included summed feature 8 (C_18:1ω7c and/or C_18:1ω6c) and C_19:0 cyclo ω8c. The predominant quinone was ubiquinone-10. The polar lipids of strain S101^T included diphosphatidylglycerol, phosphatidylglycerol, phosphatidylmethyl ethanolamine, phosphatidyl ethanolamine, amino phospholipid, unidentified phosphoglycolipid and unidentified amino-containing lipids. The DNA G + C contents of S101^T and S153 were 61.1 and 61.3 mol%, respectively. Digital DNA–DNA hybridization relatedness and average nucleotide identity values between S101^T and C. daejeonense L61^T were 46.2% and 91.4–92.2%, respectively. In addition, strain S101^T promoted the growth of soybean and carried nitrogen fixation genes in its genome, hinting at potential applications in sustainable agriculture. We propose that strains S101^T and S153 represent a novel species, named Ciceribacter sichuanensis sp. nov., with strain S101^T as the type strain (= CGMCC 1.61309 ^T = JCM 35649 ^T).