A non-symbiotic novel species, Rhizobium populisoli sp. nov., isolated from rhizosphere soil of Populus popularis.

Strain XQZ8, isolated from the rhizosphere soil of a Populus popularis plant in China, was characterized using a polyphasic taxonomic approach. Cells were Gram-negative, aerobic, non-spore-forming, and rod-shaped. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain XQZ8 was related to members of the genus Rhizobium and had the highest 16S rRNA gene sequence similarity to Rhizobium smilacinae PTYR-5 (96.6%). The average nucleotide identity and digital DNA-DNA hybridization value between strain XQZ8 and R. smilacinae PTYR-5 were 77.5% and 21.4%, respectively. TYGS whole-genome-based taxonomic and multi-locus sequence analyses of three concatenated housekeeping genes (atpD-recA-glnII) further indicated that strain XQZ8 was a new member of the genus Rhizobium. The major cellular fatty acids included summed feature 8 (C ω7c/C ω6c), summed feature 2 (C aldehyde/unknown 10.928), C, and C cyclo ω8c. The major respiratory quinones were Q-9 and Q-10. The polar lipids were phosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, phosphatidyldimethylethanolamine, phosphatidylmonomethylethanolamine, an unidentified glycophospholipid, and three unidentified lipids. The genomic DNA G + C content of the strain was 60.1 mol%. Based on the phylogenetic, phenotypic, and genotypic characteristics, strain XQZ8 represents a novel species of the genus Rhizobium, for which the name Rhizobium populisoli sp. nov. is proposed. The type strain is XQZ8 (= JCM 34442 = GDMCC 1.2201).