Putative novel Bradyrhizobium and Phyllobacterium species isolatedfrom root nodules of Chamaecytisus ruthenicus

Abstract

In this study, the diversity and the phylogenetic relationships of bacteria isolated from root nodules ofChamaecytisus ruthenicus growing in Poland were investigated using ERIC-PCR fingerprinting and by mul-tilocus sequence analysis (MLSA). Two major clusters comprising 13 and 3 isolates were detected which16S rRNA gene sequencing identified as Bradyrhizobium and Phyllobacterium. The results of phylogeneticanalysis of individual and concatenated atpD, gyrB and recA gene sequences showed that the studiedstrains may represent novel species in the genera Bradyrhizobium and Phyllobacterium. In the phyloge-netic tree based on the atpD-gyrB-recA concatemers, Bradyrhizobium isolates were split into two groupsclosely related to Bradyrhizobium algeriense STM89Tand Bradyrhizobium valentinum LmjM3T. The genusPhyllobacterium isolates formed a separate cluster close to Phyllobacterium ifriqiyense LMG27887Tin theatpD-gyrB-recA phylogram. Analysis of symbiotic gene sequences (nodC, nodZ, nifD, and nifH) showed thatthe Bradyrhizobium isolates were most closely related to Bradyrhizobium algeriense STM89T, Bradyrhizo-bium valentinum LmjM3Tand Bradyrhizobium retamae Ro19Tbelonging to symbiovar retamae. This isthe first report on the occurrence of members of symbiovar retamae from outside the Mediterraneanregion. No symbiosis related genes were amplified from Phyllobacterium strains, which were also unableto induce nodules on C. ruthenicus roots. Based on these findings Phyllobacterium isolates can be regardedas endophytic bacteria inhabitating root nodules of C. ruthenicus.