Supramolecular organization of photosynthetic complexes in membranes of Roseiflexus castenholzii

The photosynthetic membranes of the filamentous anoxygenic phototroph Roseiflexus castenholzii have been studied with electron microscopy, atomic force microscopy, and biochemistry. Electron microscopy of the light-harvesting reaction center complex produced a 3D model that aligns with the solved crystal structure of the RC–LH1 from Thermochromatium tepidum with the H subunit removed. Atomic force microscopy of the whole membranes yielded a picture of the supramolecular organization of the major proteins in the photosynthetic electron transport chain. The results point to a loosely packed membrane without accessory antenna proteins or higher order structure.