Revision of the taxonomic status of type strains of Mesorhizobium loti and reclassification of strain USDA 3471T as the type strain of Mesorhizobium erdmanii sp nov and ATCC 33669T as the type strain of Mesorhizobium jarvisii sp nov.

The species Mesorhizobim loti was isolated from nodules of Lotus comiculatus and its type strain deposited in several collections. Some of these type strains, such as those deposited in the USDA and ATCC collections before 1990, are not coincident with the original strain, NZP 2213(T), deposited in the NZP culture collection. The analysis of the 16S rRNA gene showed that strains USDA 3471(T) and ATCC 33669(T) formed independent branches from that occupied by Mesorhizobium loti NZP 2213(T) and related to those occupied by Mesorhizobium opportunistum WSM2075(T) and Mesorhizobium huakuii IFO 15243(T), respectively, with 99.9 % similarity in both cases. However, the analysis of concatenated recA, atpD and glnll genes with similarities lower than 96, 98 and 94%, respectively, between strains USDA 3471(T) and M. opportunist urn WSM2075(T) and between strains ATCC 33669(T) and M. huakuii IFO 15243(T), indicated that the strains USDA 3471(T) and ATCC 33669(T) represent different species of the genus Mesorhizobium. These results were confirmed by DNA DNA hybridization experiments and phenotypic characterization. Therefore, the two strains were reclassified as representatives of the two species Mesorhizobium erdmanii sp. nov. (type strain USDA 3471(T)=CECT 8631(T)=LMG 17826t2(T)) and Mesorhizobium jarvisii sp. nov. (type strain ATCC 33669(T)=CECT 8632(T)=LMG 28313(T)).