RESUMO
The hydrogen uptake (Hup) system of Bradyrhizobium diazoefficiens recycles the H2 released by nitrogenase in soybean nodule symbiosis, and is responsible for H2-dependent chemolithoautotrophic growth. The strain USDA110 has two hup gene clusters located outside (locus I) and inside (locus II) a symbiosis island. Bacterial growth under H2-dependent chemolithoautotrophic conditions was markedly weaker and H2 production by soybean nodules was markedly stronger for the mutant of hup locus I (ΔhupS1L1) than for the mutant of hup locus II (ΔhupS2L2). These results indicate that locus I is primarily responsible for Hup activity.
Assuntos
Bradyrhizobium/genética , Bradyrhizobium/metabolismo , Crescimento Quimioautotrófico , Hidrogênio/metabolismo , Família Multigênica , Simbiose , Bradyrhizobium/crescimento & desenvolvimento , Bradyrhizobium/fisiologia , Técnicas de Inativação de Genes , Ilhas Genômicas , Nódulos Radiculares de Plantas/microbiologia , Glycine max/microbiologiaRESUMO
Bradyrhizobium japonicum is a facultative chemolithoautotroph capable of using thiosulfate and H(2) as an electron donor and CO(2) 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 H(2) 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 CO(2) fixation for thiosulfate-dependent chemoautotrophic growth is the Calvin-Benson-Bassham cycle involving RuBisCO in B. japonicum.