Rhizobium multihospitium sp. nov., isolated from multiple legume species native of Xinjiang, China

Abstract

Thirty-one rhizobial strains isolated from nodules of legumes native of Xinjiang, China, were characterized. These strains were classified as belonging to the genus Rhizobium based on amplified 16S rDNA restriction analysis (ARDRA). The strains were distinguished from recognized Rhizobium species using analysis of 16S-23S rDNA intergenic spacers (IGS-RFLP), SDS-PAGE analysis of whole proteins and BOX-PCR; the test strains always formed a distinct cluster with patterns that were quite different from those of the reference rhizobial strains used. According to the phylogenetic analysis based on the 16S rRNA gene, the test strains belonged to the genus Rhizobium, with Rhizobium tropici, Rhizobium rhizogenes and Rhizobium lusitanum as the closest related species, with 99.6, 99.2 and 99.4 % sequence similarities, respectively, between the type strains of the three Rhizobium species and strain CCBAU 83401(T). Phylogenetic analyses of the representative strains using IGS and atpD, recA and glnII genes all confirmed the phylogenetic arrangements obtained using the 16S rRNA gene. The DNA-DNA relatedness values between strain CCBAU 83401(T) and strains CCBAU 83364, CCBAU 83345 and CCBAU 83523 ranged from 80.8 to 100 %, showing that they belong to the same species. The DNA-DNA relatedness between strain CCBAU 83401(T) and R. tropici IIB CIAT 899(T), R. tropici IIA CFN 299, R. rhizogenes LMG 150(T) and R. lusitanum P1-7(T) were 26.9, 27.7, 38.2 and 22.6 %, respectively, clearly indicating that strain CCBAU 83401(T) represents a novel species. Phenotypic characterization of four representative strains, CCBAU 83401(T), CCBAU 83364, CCBAU 83345 and CCBAU 83523, showed several distinctive features that differentiated them from closely related species. The 31 strains had identical nodD and nifH genes, which were very similar to those of the bean-nodulating R. lusitanum, Devosia neptuniae and R. tropici IIB. Based upon these results, the strains from this study are considered to represent a novel species, for which the name Rhizobium multihospitium sp. nov. is proposed. The DNA G+C content ranged from 65.3 to 66.0 mol% (T(m)). The type strain is CCBAU 83401(T) (=LMG 23946(T)=HAMBI 2975(T)), which nodulates Robinia pseudoacacia, but not Leucaena leucocephala, Phaseolus vulgaris, Pisum sativum or Medicago sativa.