Characterization of root-nodule bacteria isolated from the medicinal legume Indigofera tinctoria

Abstract

Fourteen root-nodule bacteria isolated from the medicinal legume Indigofera tinctoria were characterized for their phenotypic features including growth curves, utilization of carbon and nitrogen sources, antibiotic resistance, vitamin requirement and growth under different conditions. The partial sequences of the 16S rDNA of these strains were obtained and BLASTN analysis revealed that the microsymbionts of I. tinctoria were related to members of five distinct genera: Rhizobium, Sinorhizobium, Bradyrhizobium, Cupriavidus and Pseudoalteromonas. The partial nifH gene of Pseudoalteromonas-like strain DASA 57075 had 96% similarity with nifH genes of members of Bradyrhizobium. The partial nodC gene of Pseudoalteromonas-like strain DASA 57075 showed 88% similarity with the nodC gene of several rhizobia including Sinorhizobium, Bradyrhizobium and Mesorhizobium. We propose a bacterium that is related to Pseudoalteromonas from the gamma-class of Proteobacteria as a new legume symbiont. This is also the first report that the same species of legume can be nodulated by bacteria from up to five different genera in three distinct classes. © 2010 Springer-Verlag and the University of Milan.