Rhizobium panacihumi sp. nov., an isolate from ginseng-cultivated soil, as a potential plant growth promoting bacterium.

A novel bacterial strain designated DCY116T was isolated from ginseng-cultivated soil in Gochang-gun, Republic of Korea. Strain DCY116T, belongs to the genus Rhizobium, and is closely related to Rhizobium yantingense H66T (98.3%), Neorhizobium huautlense S02T (98.2%), Rhizobium soli DS-42T (98.1%), Rhizobium smilacinae PTYR-5T (97.9%), and Neorhizobium alkalisoli CCBAU 01393T (97.9%) based on 16S rRNA gene sequence analysis. Analysis of the housekeeping genes atpD, recA, and glnII showed low levels of sequence similarity (96.8%) between strain DCY116T and other closely related species. Strain DCY116T was Gram-stain negative, motile by peritrichous flagella, rod-shaped, strictly aerobic, catalase- and oxidase-positive. Q-10 was the predominant ubiquinone. The major cellular fatty acids were identified as C16:0 and summed feature 8 (C18:1 ω7c and/or C18:1 ω6c). The major polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, and an unknown lipid (L1-3). Genomic DNA G + C content of strain DCY116T was determined to be 57.2 mol%. DNA-DNA homology values between strain DCY116T and closely related species of the genus Rhizobium were lower than 40%. Strain DCY116T produced indole-3-acetic acid, siderophores, and was able to solubilize phosphate as a potential plant growth promoting bacterium. In conclusion, the results of this study support strain DCY116T as a novel species of the genus Rhizobium, for which the name Rhizobium panacihumi is proposed. The type strain is DCY116T (= KCTC 62017T = JCM 32251T).