INFLUENCE OF LIGHT ON THE EPR-DETECTABLE, ELECTRON TRANSPORT COMPONENTS IN WHOLE CELL RHODOSPIRILLUM RUBRUM

Abstract —The influence of light upon the electron paramagnetic resonance (EPR)-active components of R. rubrum , both in whole cells and in subcellular particle preparations, is presented. In the whole cells, 16 EPR signals can be detected, 11 of which are influenced by illumination of the bacteria. Four of these are also affected by illumination at 77 K. The effects of K₃Fe(CN)₆, Na₂S₂O₄ and heating upon the signals observed in the whole cells are also presented. The whole cells contain several photoinfluenced, EPR-active components that are missing in the subcellular particle preparations. The kinetics of most of the signals in the whole cells are complex, whereas in the subcellular particles the kinetics are generally monotonic. For comparison, some of the EPR signals detected in whole-cell Chromatium D are also presented. The signals observed in these two strains of bacteria differ considerably. A discussion of the possible identities of the R. rubrum signals and speculation as to the role of some of them in the photosynthetic electron transport system are also included.