scytonemine

Scytonemin is a yellowish-brown pigment produced by many species of cyanobacteria. It is a type of scytonemin, a class of extracellular polymeric substances (EPS) that accumulate in the sheaths of cyanobacterial cells. The pigment plays a significant role in protecting cyanobacteria from environmental stressors, particularly UV radiation.

The chemical structure of scytonemin is characterized by a planar, fused-ring system that efficiently absorbs ultraviolet and visible light. This absorption capability is crucial for organisms living in environments exposed to high levels of solar radiation, such as arid soils, deserts, and shallow waters. By absorbing UV-B and UV-A radiation, scytonemin prevents damage to cellular components like DNA and proteins, thereby enhancing survival rates.

Scytonemin is often visible as a colored sheath or layer surrounding the cyanobacterial colonies, giving them a distinct brown or yellow appearance. Its production can be induced by exposure to light, particularly UV light, and also by desiccation. This pigment is an important component of the cyanobacterial extracellular matrix, contributing to structural integrity and water retention in addition to photoprotection. Its presence is a key characteristic used in the identification and classification of certain cyanobacterial taxa. Researchers are also exploring the potential applications of scytonemin, including its use as a natural sunscreen or as a component in bio-based materials due to its protective properties.