Abstract
Green photosynthetic bacteria harvest light and perform photosynthesis in low light environments, and contain specialized antenna complexes to adapt to this condition. In this report, we present studies using small-angle neutron scattering (SANS) to elucidate structural information about the photosynthetic apparatus, including the peripheral light harvesting chlorosome complex, the integral membrane light-harvesting B808-866 complex and the reaction center (RC) in the thermophilic green phototrophic bacterium Chloroflexus aurantiacus. Using contract variation in SANS measurments, our studies suggest that the B808-866 comples is wrapped around the RC in Cfx. aurantiacus, and the overall size and conformation for the B808-866 complex of Cfx. aurantiacus is roughly comparable to the LH1 antenna complex of the purple bacteria. A similar size for the isolated B808-866 complex is also suggested via dynamic light scattering measurements. Alos, a smaller size of the RC of Cfx. aurantiacus that the RC of the purple bacteria is observed. Further, our SANS measurements indicate that the chlorosome is a lipid body with rod-like shape, and that the self-assembly of bacteriochlorophylls, the major component of the chlorosome, is lipid-like. Finally, two populations of chlorosome particles are suggested in our SANS measurements.
