Transposon Tn5 Mutagenesis of Bradyrhizobium japonicum: A Histidine Auxotrophic Mutant of B. japonicum Shows Defective Nodulation Phenotype on Soybean

Transposon Tn5 was used to induce random insertional mutations in Bradyrhizobium japonicum, a soybean endosymbiont. By genomic Southern blot analysis, transposition events were found to have occurred randomly throughout the B. japonicum genome. After screening 3, 626 mutants by auxotrophy test, a histidine auxotroph was isolated. Upon plant infection test, the His mutant showed a 3~4 day delay in nodule formation.