Rhizobium zeae sp nov., isolated from maize (Zea mays L.) roots

A bacterial strain designated CRZM18R(T) was isolated from a root of Zea mays in Spain. The analysis of the 16S rRNA gene sequence showed that this strain belongs to the genus Rhizobium, with Rhizobium cellulosilyticum ALA10B2(T) and Rhizobium yantingense H66(T) being the most closely related species with 98.3 and 97.9% sequence similarity, respectively. The analysis of the concatenated recA and atpD genes showed that strain CRZM18R(T) forms a cluster with these species and also with Rhizobium smilacinae PTYR-5(T), but the recA and atpD genes of strain CRZM18R(T) were phylogenetically distant, with identities lower than 90 and 96 %, respectively. DNA-DNA hybridization analysis showed mean relatedness of 43, 22 and 38% with respect to R. cellulosilyticum ALA10B2(T), R. yantingense LMG 28229(T) and R. smilacinae LMG 27604(T). Phenotypic characteristics also differed from those of the most closely related species of the genus Rhizobium. The major fatty acids were those from summed feature 8 (C-18 (:1)omega 6c/C-18: (1)omega 7c) and C-16: 0. Based on the genotypic, chemotaxonomic and phenotypic data obtained in this study, we propose to classify strain CRZM18R(T) in a novel species named Rhizobium zeae sp. nov. (type strain CRZM18R(T)= LMG 29735(T)=CECT 9169(T)).