The photosynthetic bacteria respire without oxygen. No oxygen is evolved in bacterial photosynthesis. Water is not used as a source of reducing power. Instead, hydrogen is obtained either directly or from various types of inorganic and organic compounds, e.g., H2​S, aliphatic compounds. Anoxygenic photosynthesis is characteristic of Rhodospirillum. It is a non-oxygenic photosynthetic bacteria.