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 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 showed 98.4% sequence similarity to the closest type strain, Ciceribacter daejeonense L61. Major cellular fatty acids in strain S101 included summed feature 8 (Cω7c and/or Cω6c) and C cyclo ω8c. The predominant quinone was ubiquinone-10. The polar lipids of strain S101 included diphosphatidylglycerol, phosphatidylglycerol, phosphatidylmethyl ethanolamine, phosphatidyl ethanolamine, amino phospholipid, unidentified phosphoglycolipid and unidentified amino-containing lipids. The DNA G + C contents of S101 and S153 were 61.1 and 61.3 mol%, respectively. Digital DNA-DNA hybridization relatedness and average nucleotide identity values between S101 and C. daejeonense L61 were 46.2% and 91.4-92.2%, respectively. In addition, strain S101 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 and S153 represent a novel species, named Ciceribacter sichuanensis sp. nov., with strain S101 as the type strain (= CGMCC 1.61309 = JCM 35649).