Soybean (Glycine max) is considered one of the most economically important agricultural crops in Brazil. Due to the high protein content of its grains, this crop demands a greater amount of nitrogen (N) for production. In general, for soybean, nitrogen fertilization costs through chemical fertilizers are considered high. However, the biological nitrogen fixation (BNF) through the use of biological inoculants, such as the strains of Bradyrhizobium genus, a rhyzobacterium, represents a viable alternative for soybean crops in Brazil and dismisses nitrogen fertilization. Because of the need to constantly increase soybean crop productivity, it is necessary to find more efficient Bradyrhizobium genus strains for BNF. Genes related to soybean BNF have been utilized as molecular markers in selection programs that aim to obtain more efficient bacterial strains in this process. Therefore, this study aimed to characterize the gens related to BNF efficiency (nopP, aapP, ilvD and bll3106) by PCR-RFLP in Bradyrhizobium japonicum strains. The nopP and aapP genes were sequenced and submitted to similarity analysis with genes deposited on the Genbank (NCBI). The results showed the presence of highly conservative sequences in nopP and aapP genes between the analyzed B. japonicum strains. The occurrence of these preserved nucleotide sequences can be related to the adaptive function that they can have during the evolutionary process of plant growth promoting rhizobacteria.