TRAPPING AND CHARGE STABILIZATION IN CHLOROSOME CONTAINING BACTERIA -COMPARATIVE-STUDY ON CHLOROFLEXUS-AURANTIACUS AND CHLOROBIUM-LIMICOLA

Trapping and charge stabilization in intact cells of Chloroflexus aura ntiacus and Chlorobium limicola were studied by means of photovoltage kinetics and fluorescence emission spectra upon excitation in the chlo rosome. In Chloroflexus two electrogenic phases with time constants of 100 ps for trapping (P+ H- formation) from the core-complexes and 530 ps for charge stabilization (Q(A) reduction) were found. In Chlorobiu m there were also two electrogenic phases of 105 ps and 650 ps. The la ter phase most likely represents the charge stabilization on the iron- sulfur center, F-X. A comparison of stationary fluorescence spectra of both species indicates that the trapping time from the core pigments in Chlorobium is significantly faster than in Chloroflexus. This prove s the existence of at least two intermediary accepters between the pri mary donor (P 840) and F-X in the Chlorobium reaction center. In both species the photovoltage signal in the low excitation limit appeared a fter a lag phase of 55 to 65 ps, which is ascribed to the energy trans fer from the chlorosome to the core pigments.