Identification of the primary electron donor in PSII of the Chl d-dominated cyanobacterium Acaryochloris marina

The primary electron donor of photosystem (PS) II in the chlorophyll (Chl) d-dominated cyanobacterium Acaryo-chloris marina was confirmed by delayed fluorescence (DF) and further proved by pigment contents of cells grown under several light intensities. The DF was found only in the Chl a region, identical to Synechocystis sp. PCC 6803, and disappeared following heat treatment. Pigment analyses indicated that at least two Chl a molecules were present per each two pheophytin a molecules, and these Chl a molecules are assigned to P-D1 and P-D2. These findings clearly indicate that Chl a is required for water oxidation in PS II. (C) 2003 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.