The cbbL gene is required for thiosulfate-dependent autotrophic growth of Bradyrhizobium japonicum

Bradyrhizobium japonicum is a facultative chemolithoautotroph capable of using thiosulfate and H₂ as an electron donor and CO₂ as a carbon source. In B. japonicum USDA110, the mutant of cbbL gene encoding a large subunit of ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBisCO) was unable to grow using thiosulfate and H₂ as an electron donor. The cbbL deletion mutant was able to grow and oxidize thiosulfate in the presence of succinate. These results showed that the major route of CO₂ fixation for thiosulfate-dependent chemoautotrophic growth is the Calvin-Benson-Bassham cycle involving RuBisCO in B. japonicum.