S-layer

Definition

The S-layer (surface layer) is a crystalline array of protein or glycoprotein that covers the surface of many prokaryotic cells, providing structural support and protection. It is one of the outermost layers in these cells, often associated with cell wall integrity and interaction with the environment.

5 Must Know Facts For Your Next Test

1. S-layers are composed of proteins or glycoproteins that form a regular, repeating pattern.
2. They can serve as a selective sieve for molecules entering or leaving the cell.
3. S-layers provide protection against environmental stress, including changes in pH, osmotic pressure, and enzymatic degradation.
4. In some bacteria and archaea, the S-layer is involved in adhesion to surfaces and biofilm formation.
5. The presence and structure of an S-layer can be identified through electron microscopy.

Review Questions

• What are the primary components that make up an S-layer?
• How does the S-layer contribute to a prokaryotic cell's interaction with its environment?
• What techniques are used to identify and study S-layers in prokaryotic cells?

Related terms

Peptidoglycan:

A polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of most bacteria.

Capsule:

A gelatinous layer forming the outermost part of some bacterial cells, aiding in protection and adherence.

Biofilm:

A complex aggregation of microorganisms growing on a solid substrate, encased within a self-produced extracellular matrix.