Rhizobium rhizolycopersici sp. nov., Isolated from the Rhizosphere Soil of Tomato Plants in China.

During characterization of rhizobacteria, strain DBTS2 was isolated from the rhizosphere soil samples of healthy tomato plants and characterized using a polyphasic taxonomic approach. Phylogenetic analysis using 16S rRNA gene sequences showed this strain belonged to the genus Rhizobium and was most closely related to Rhizobium subbaraonis JC85 (99.1%) and Rhizobium daejeonense CCBAU 10050 (97%). Cells of strain DBTS2 were Gram-negative, short rod, aerobic and non-motile. This novel strain was found to grow at 20-45 °C (optimum 25-37 °C), pH 5-9 (optimum 8) and in the presence of 4% NaCl. It was positive for catalase and oxidase. The predominant cellular fatty acids were Summed Feature 8 (52.7%) and C cyclo ω8c (23.3%). The polar lipids of strain DBTS2 consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, unidentified aminophospholipid, unidentified aminolipid, four unidentified phospholipids, unidentified lipid, phosphatidylcholine, unknown glycolipid and unknown aminophosphoglycolipids. Q-10 was the major quinone. The DNA-DNA hybridization similarity values between the strain DBTS2 and R. subbaraonis JC85, R. daejeonense CCBAU 10050 and Rhizobium azooxidifex DSM100211 were 46.4%, 20.7% and 25.5%, respectively. The ANI value was 91.96% between strain DBTS2 and R. subbaraonis JC85 and 75.18% between strain DBTS2 and R. daejeonense CCBAU 10050. The DNA G+C content of the genomic DNA was 63.1 mol%. Based on these results, it was concluded that the isolate represents a novel species of the genus Rhizobium, for which the name Rhizobium rhizolycopersici sp. nov. is proposed, with DBTS2 (= CICC 24887 = ACCC61707 = JCM 34245) as the type strain.