Chlorosome

Chlorosome is a unique type of light-harvesting complex found in green sulfur bacteria and some green filamentous anoxygenic phototrophs. Unlike other light-harvesting complexes in photosynthetic organisms, chlorosomes are large, membrane-enclosed structures that directly capture light and transfer its energy with high efficiency. They are particularly adept at capturing low levels of light, which is why organisms containing chlorosomes can thrive in extremely low-light environments, such as deep in the ocean or under thick layers of ice.

Structure

Chlorosomes are ellipsoidal bodies that are attached to the cytoplasmic side of the inner cell membrane. They are enclosed by a lipid monolayer rather than a bilayer, which is unique among photosynthetic membranes. Inside, chlorosomes contain a dense array of bacteriochlorophyll molecules, which are responsible for capturing light. The arrangement of these molecules allows for a very efficient transfer of energy towards the reaction center of the cell.

Function

The primary function of chlorosomes is to absorb light and transfer the energy to the photosynthetic reaction centers where it can be used to drive the synthesis of ATP and NADPH, the energy currency of the cell. Chlorosomes are capable of absorbing light across a wide spectrum, but they are especially efficient in capturing wavelengths that penetrate deep water, such as green and near-infrared light. This capability allows chlorosome-containing bacteria to perform photosynthesis in conditions where light is scarce.

Ecological Significance

Chlorosomes enable green sulfur bacteria and green filamentous anoxygenic phototrophs to inhabit and thrive in low-light environments. This adaptation has significant ecological implications, as these bacteria form the basis of the food web in such ecosystems. By converting light into chemical energy, they support a variety of life forms, including higher organisms that depend on the organic compounds produced by photosynthesis.

Research and Applications

Research into chlorosomes and their unique light-harvesting capabilities is ongoing, with potential applications in the field of bio-inspired solar energy. Understanding how chlorosomes capture and transfer light with such high efficiency could inform the design of more efficient solar panels and other light-harvesting technologies.

See Also

• Photosynthesis
• Bacteriochlorophyll
• Green sulfur bacteria
• Bio-inspired solar energy