Uphill energy transfer in a chlorophyll d-dominating oxygenic photosynthetic prokaryote, Acaryochloris marina

The steady-state fluorescence properties and uphill energy transfer were an alyzed on intact cells of a chlorophyll (Chl) d-dominating photosynthetic p rokaryote, Acaryochloris marina. Observed spectra revealed clear difference s, depending on the cell pigments that had been sensitized; using these pro perties, it was possible to assign fluorescence components to specific Chi pigments. At 22 degrees C, the main emission at 724 nm came from photosyste m (PS) II Chi LJ, which was also the source of one additional band at 704 n m. Chi a emissions were observed at 681 nm and 671 nm. This emission patter n essentially matched that observed at -196 degrees C. as the main emission of Chi d was located at 735 nm, and three minor bands were observed at 704 nm, 653 nm, and 667 nm, originating from Chi d Chi a, and Chi a, respectiv ely. These three minor bands, however, had not been sensitized by carotenoi ds, suggesting specific localization in PS II. At 22 degrees C, excitation of the red edge of the absorption band (which, at 736 nm, was 20 nm longer than the absorption maximum): resulted in fluorescence bands of Chi d at 72 4 nm and of Chi a at 682 nm, directly demonstrating an uphill energy transf er in this alga. This transfer is a critical factor for in vivo activity, d ue to an inversion of energy levels between antenna Chi d and the primary e lectron donor of Chi a in PS II. (C) 2000 Elsevier Science B.V. All rights reserved.