Transmission Electron Microscopic Study on Supramolecular Nanostructures of Bacteriochlorophyll Self-Aggregates in Chlorosomes of Green Photosynthetic Bacteria

摘要

Supramolecular nanostructures of bacteriochlorophyll (BChl) self-aggregates in major light-harvesting complexes (chlorosomes) of green photosynthetic bacteria were successfully observed by freeze-fracture transmission electron microscope.Rod-shaped nanostructures with approxi-mately 10 nm in diameter could be visualized in three types of green sulfur bacteria {Chlorobium).Diameter of the rod-shaped nanostructures in Chlorobium chlorosomes was independent of the molecular structures of their light-harvesting pigments,namely BChl-c or d.In contrast,chloro-somes of the green filamentous bacterium Chloroflexus aurantiacus had rod-shaped nanostruc-tures with approximately 5 nm in diameter.The present results support that BChl self-aggregates in chlorosomes form rod-shaped nanostructures called rod-elements with approximately 10-and 5-nm diameters for Chlorobium and Chloroflexus,respectively.