Utilization of reducing power in light-limited cultures of Chromatium vinosum DSM 185

This study describes how the phototrophic organism Chomatium vinosum, when grown under different degrees of light limitation, distributes the reducing power initially present in the medium as hydrogen sulfide. Under all the conditions of illumination tested, sulfur was the major store of reducing power. Glycogen, which was virtually absent under light limitation, accounted for 31.6% of the stored reducing power at saturating irradiances. Analysis of the electron budget showed that under light-limiting conditions, an important fraction of reducing power did not appear in storage products or in structural cell material. Analysis of dissolved organic carbon in the supernatant of the culture indicated the excretion of organic compounds.