What are S layers (Surface layer) in bacterial cell envelope?
S-layer (surface layer proteins) is a regularly structured crystalline layer present on the surface of many bacteria and archaebacteria.
Chemical nature:
The S-layer is composed of protein or glycoprotein.
Location: In Gram positive bacteria, S-layer is associated with peptidoglycan surface.
In Gram negative bacteria, it is associated with the outer membrane (lipopolysaccharide layer)
Biological Functions:
- Protecting cell against ion and pH fluctuations, osmotic stress, degrading enzymes or predacious bacteria.
- Helps in maintaining shape and envelope rigidity of the cell
- It promote cell adhesion to surfaces
- It contributes to the virulence of bacteria.
- Widely studied recently especially in connection with nanotechnology due to their ability to self assemble protein units without the aid of enzymes.
Future prospects: S-layer could be used technologies such as drug delivery systems and novel detection systems for toxic chemicals.
