The ability of photosynthetic Bradyrhizobium strains ORS285 and ORS278 to nodulate soybeans was investigated. While the nod gene-deficient ORS278 strain induced bumps only on soybean roots, the nod gene-containing ORS285 strain formed nitrogenfixing nodules. However, symbiotic efficiencies differed drastically depending on both the soybean genotype used and the culture conditions tested.