Most bacteria have the capability to adapt to changes in their environment. Facultatively phototrophic bacteria like Rhodobacter can switch from aerobic respiration to anoxygenic photosynthesis in the absence of oxygen. The formation of the photosynthetic apparatus is primarily regulated by oxygen tension. The amount of photosynthetic complexes is influenced by the light intensity in anaerobic cultures. This review focuses on the molecular mechanisms involved in the regulation of Rhodobacter photosynthesis genes by oxygen and light.