Independently Acting Oxygen-Forming Complexes of Photosystem II in Cyanobacteria A Study in the Filamentous Cyanobacterium Oscillatoria chalybea

It has been postulated that the oxygen-evolving centers of photosystem II do not operate independently in the cyanobacterium Synechococcus leopoliensis in contrast to those of the chlorophyte Chlorella vulgaris and the diatom Phaeodactylum tricornutum (Mauzerall and Dubinsky (1993), Biochim. Biophys. Acta 1183, 123-129). Dependence would mean the exis­ tence of charge transfer among adjacent units and would be manifested by different satura­ tion curves for the individual flashes of a sequence (different cross-sections), stronger damped oscillations and oxygen formation under the first flash, independently of the length of dark adaptation. We show in the present publication that in the filamentous cyanobacter­ ium Oscillatoria chalybea the 0 2-evolution pattern which shows an 0 2-signal under the first flash (despite dark adaptation) can be explained within the heterogeneous Kok-model, as­ suming a non-standard initial S-state distribution (Bader, Thibault and Schmid (1983), Z. Naturforsch. 38c. 778-792).