Purple bacteria or purple photosynthetic bacteria are proteobacteria that are phototrophic, that is, capable of producing energy through photosynthesis. They may be divided into two groups purple sulfur bacteria and purple non-sulfur bacteria. Like most other photosynthetic bacteria, purple bacteria do not produce oxygen, because the reducing agent (electron donor) involved in photosynthesis is not water. In some, called purple sulfur bacteria, it is either sulfide or elemental sulfur. The others, called purple non-sulfur bacteria, typically use hydrogen although some may use other compounds in small amounts. Thus, option A is correct. In higher plants and cyanobacteria, breakdown of water takes place during photosynthesis. Thus, option B and C are incorrect.