Abstract

Chlorobium limicola is a green sulfur photosynthetic bacteria. Its light harvesting system consists of huge extra-membrane ellipsoidal structures (100-150 nm long and 30-40 nm in diameter) called chlorosomes. Each chlorosome contains several thousands of bacteriochlorophyll-c (BChl-c) molecules (organized in long rod-like pigment-protein complexes) together with a significant amount of carotenoids. The whole chlorosome is enveloped with a BChl-a containing layer and attached to the cytoplasmic membrane through a water soluble BChl-a polypeptide link complex. Light energy absorbed in BChl-c is transfered via BChl-a in the envelope and via BChl-a in the link polypeptide complex to the BChl-a containing core antenna which surrounds the reaction center and is located within the cytoplasmic membrane. In the last few years, the dynamics of the excited energy transport (EET) in the whole light harvesting system of Chlorobium limicola and related species have been extensively studied. Fast EET from BChl-c to BChl-a was studied by means of ps absorption [1] and ps fluorescence decay [2]. Both methods yield similar values of the shortest decay components which characterize the EET: 21 ps and 26 ps, respectively. Detailed hole burning study of the BChl-a containing link antenna of Prosthecochloris aestuarii revealed excitonic structure of the antenna subunits and provided the decay times (on the order of 100 fs) of upper excitonic levels [3].

© 1992 Optical Society of America