FIG. 5.

Mechanisms involved in adaptation of the efficiency of energy conservation to intracellular requirements under photoautotrophic (A) and photoheterotrophic (B) growth conditions. Cyclic photosynthetic electron transport and the specific redox-balancing mechanisms of the CBB, DMSOR, and nitrogenase systems contribute to redox homeostasis in R. capsulatus. NADH generated by the oxidation of carbon substrates or reverse electron flow via complex I is dissipated by the CBB system (A and B) and perhaps the nitrogenase system (B). Flux of reductant from the ubiquinone pool is transduced to the DMSOR system under phototrophic growth conditions (A and B). The dotted line indicates the influence of DMSO reduction on specific redox-balancing mechanisms under phototrophic environmental conditions (A and B).