Cells of phototrophic bacterla are fitted out with a characteristic and sometimes species-specific membrane-system: the continuous but differ- ently composed cytoplasmic-intracytoplasmic membrane systems in purple bacteria, the cytoplasmic membrane with the attached light-harvesting chlorosomes in green bacteria and the intracytpplasmic thylakoids with the attached light-harvesting phycobilisomes in cyanobacteria. During the long-lasting evolutionary process phototrophic bacteria have been adapted to numerous ecological niches and on this way they have developed various types of...