Mesorhizobium helmanticense sp nov., isolated from Lotus corniculatus nodules

In this study, three strains belonging to the genus Mesorhizobium, CSLC115N(T), CSLC19N and CSLC37N, isolated from Lotus corniculatus nodules in Spain, were characterized. Their 16S rRNA gene sequences were closely related to those of Mesorhizobium metallidurans STM 2683(T), Mesorhizobium tianshanense A-1BS(T), Mesorhizobium tarimense CCBAU 83306(T), Mesorhizobium gobiense CCBAU 83330(T) and Mesorhizobium caraganae CCBAU 11299(T) with similarity values higher than 99.7%. The analysis of concatenated recA and glnII genes showed that the most closely related type strains were M. metallidurans STM 2683(T), M. tianshanense A-1BST and M. tarimense CCBAU 83306T with 96, 95 and 94% similarity values in the recA gene and 95, 94 and 94% in the glnII gene, respectively. M. metallidurans LMG 24485(T), M. tianshanense USDA 3592(T) and M. tarimense LMG 24338(T) showed means of 44, 41 and 42% DNA-DNA relatedness, respectively, with respect to strain CSLC115N(T). The major fatty acids were those from summed feature 8 (C-18: (1) omega 7c/C-18: (1)omega 6c), C-16: (0) and C-18: (1)omega 7c 11-methyl. The results of phenotypic characterization support that the L. corniculatus nodulating strains analysed in this work belong to a novel species of the genus Mesorhizobium for which the name Mesorhizobium helmanticense sp. nov. is proposed, and the type strain is CSLC115N(T)(= LMG 29734(T)= CECT 9168(T)).