Up-regulated expression of the cbb(I) and cbb(II) operons during photoheterotrophic growth of a ribulose 1,5-bisphosphate carboxylase-oxygenase deletion mutant of Rhodobacter sphaeroides

In a Rhodobacter sphaeroides ribulose 1,5-bisphosphate carboxylase-oxygenase deletion strain that requires an exogenous electron donor for photoheterotrophic growth, transcription of the genes of the Calvin-Benson-Bassham (CBB) cycle was increased. This finding pointed to a potential physiological effector that enhances the capability of the positive transcriptional activator CbbR to mediate cbb transcription. This effector is most likely ribulose 1,5-bisphosphate or a metabolite derived from this CBB pathway intermediate.