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

A novel bacterial strain designated DCY116 was isolated from ginseng-cultivated soil in Gochang-gun, Republic of Korea. Strain DCY116 belongs to the genus Rhizobium, and is closely related to Rhizobium yantingense H66 (98.3%), Neorhizobium huautlense S02 (98.2%), Rhizobium soli DS-42 (98.1%), Rhizobium smilacinae PTYR-5 (97.9%), and Neorhizobium alkalisoli CCBAU 01393 (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 DCY116 and other closely related species. Strain DCY116 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 C and summed feature 8 (C ω7c and/or C ω6c). The major polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, and an unknown lipid (L1-3). Genomic DNA G + C content of strain DCY116 was determined to be 57.2 mol%. DNA-DNA homology values between strain DCY116 and closely related species of the genus Rhizobium were lower than 40%. Strain DCY116 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 DCY116 as a novel species of the genus Rhizobium, for which the name Rhizobium panacihumi is proposed. The type strain is DCY116 (= KCTC 62017 = JCM 32251).