| Photosynthesis, the capture and conversion of light energy, is an essential process for life on Earth. The physiological and structural features that allow green sulfur bacteria to perform photosynthesis efficiently in anaerobic conditions are the topic of this dissertation.; The green sulfur bacteria shows modulation in fluorescence yield that can be linked to cellular physiology. The fluorescence yield of the FMO-protein is the most modulated fluorescence component. This modulation is dependent on the availability of an excitation quencher that shows pool features, and can be depleted through strong illumination and by limiting membrane diffusion. This quencher might be menaquinone that could act by direct quenching on the FMO-protein, or by modulating the reaction center, which is energetically coupled to the FMO-protein.; Electron tomography studies show that chlorosomes, the main antenna system of green sulfur bacteria, exhibit heterogeneity in the degree of membrane association, morphology and volume. Most chlorosomes possess an electron transparent area that might indicate an uneven distribution of bacteriochlorophyll. Chlorosomes appear to be part of a structural network that includes outer membrane, inner membrane, inclusions, and the central granules, all linked by filament-like elements. These filament-like elements permeate the central granules, which are present in each cell. A combination of electron energy loss spectroscopy and electron diffractive x-ray analysis identified these granules as phosphate bodies. |
