The photosystem of the green sulfur bacterium Chlorobium limicola contains two early electron acceptors similar to photosystem I

AbstractAn asymmetric EPR-line with a g factor of 2.0045 was detected after phototrapping at 196 K in membranes and in isolated photoactive P840 reaction centers of Chlorobium limicola f. thiosulfatophilum. The spectra resemble those of the electron acceptor A−1 of photosystem I in chloroplasts and cyanobacteria. At 229 K a symmetric signal at g=2.0033, comparable to the one of the early electron acceptor A−0 is additionally phototrapped. In contrast to membranes, the reaction center preparation does not contain appreciable amounts of photoreducible FeS-centers