Photosynthetic bacteria are a group of bacteria that contain light absorbing pigments (chlorophyll or bacteriochlorophyll), which makes them capable of converting light energy into chemical energy. These include cyanobacteria, purple bacteria, green sulphur bacteria, heliobacteria and green gliding bacteria.
Although photosynthesis is most commonly associated with plants and algae, much of our understanding about how photosynthetic organisms harvest sunlight and convert it to more useful forms can be attributed to research involving photosynthetic bacteria. Research has shown that the process of photosynthesis in purple non-sulphur bacteria (Rhodospirillaceae) is similar to photosynthesis in green plants but is less complicated and better understood.
Photosynthesis in bacteria takes place in plasma membranes unlike photosynthesis in plants which takes place in chloroplasts. Cyanobacteria contain chlorophyll while other forms of bacteria contain bacteriochlorophyll. Bacteriochlorophyll a is the most common form of bacteriochlorophyll but other forms include b, c, d, e, f and g. Although bacteriochlorophyll resembles chlorophyll in cyanobacteria and plants, it absorbs light with wavelengths between 800-925nm. Chlorophyll absorbs light with wavelengths between 450-650nm.
Bacteria that contain bacteriochlorophyll do not use water as an electron donor and therefore do not produce oxygen. This is known as anoxygenic photosynthesis. Cyanobacteria perform photosynthesis using water as an electron donor in a similar manner to plants. This results in the production of oxygen and is known as oxygenic photosynthesis.
Classification of Photosynthetic Bacteria
The slide presentation below provides additional information about photosynthetic bacteria.
Useful Applications for Photosynthetic Bacteria
Photosynthetic bacteria are currently being used in various applications which include water purification, bio-fertilizers, animal feed and bioremediation of chemicals among many others. They are used in the treatment of polluted water since they can grow and utilize toxic substances such as H2S or H2S203.
Researchers at Harvard’s Wyss Institute have engineered photosynthetic bacteria to produce simple sugars and lactic acid. In the video below, Dr. Jeffrey Way explains the science behind the innovation and the potential benefits of this technology.