Index >> Bacterial Taxonomy >> Phototrophic Bacteria

All con­tain bacterial chlorophylls a, b, c, and d. Photosynthesis occurs under anaerobic conditions. Electron donors in photosynthesis are reduced sulphur compounds, molecular hydrogen or organic compounds. Some species fix molecular nitrogen. DNA base ratios vary from 45-73 moles % G + C.

The phototrophic bacteria consist of two separate groups; the purple bacteria and the green sulphur bacteria. The purple bacteria are further subdivided into purple non sulphur and purple sulphur bacteria. Organic substances serve both as carbon source and as hydrogen donors for the reduction of carbon dioxide. They do not generally oxidize inorganic sulphur compounds. Some species are capable of growing aerobically in the dark and these obtain their energy from the oxidation of organic compounds. The purple sulphur bacteria: (Chromatiaceae) exhibit a variety of shapes ranging from spheres to rods or spirals