Anoxygenic photosynthesis

Anoxygenic Photosynthesis is a form of photosynthesis in which oxygen is not produced. This process is carried out by certain types of bacteria, such as purple bacteria and green sulfur bacteria. Unlike oxygenic photosynthesis, which is performed by plants, algae, and cyanobacteria, anoxygenic photosynthesis uses electron donors other than water.

Process

The process of anoxygenic photosynthesis is similar to oxygenic photosynthesis in that it involves the absorption of light by photosynthetic pigments and the transfer of electrons to create a proton gradient. This gradient is then used to generate adenosine triphosphate (ATP), the energy currency of the cell. However, the electron donors used in anoxygenic photosynthesis can vary and include substances such as hydrogen sulfide, sulfur, and ferrous iron.

Types of Bacteria

There are several types of bacteria that perform anoxygenic photosynthesis. These include:

• Purple bacteria: These bacteria use hydrogen sulfide or organic molecules as their electron donors. They contain a type of photosynthetic pigment known as bacteriochlorophyll, which absorbs light in the infrared spectrum.

• Green sulfur bacteria: These bacteria use hydrogen sulfide as their electron donor and produce sulfur as a byproduct. They contain bacteriochlorophyll and absorb light in the infrared spectrum.

• Heliobacteria: These bacteria use organic molecules as their electron donors. They contain a type of photosynthetic pigment known as bacteriochlorophyll g, which absorbs light in the infrared spectrum.

Ecological Significance

Anoxygenic photosynthesis plays a significant role in the carbon cycle, as it helps to convert carbon dioxide into organic compounds. It also contributes to the sulfur cycle, particularly in environments where oxygen is scarce.

See Also

• Photosynthesis
• Oxygenic photosynthesis
• Bacteria
• Carbon cycle
• Sulfur cycle