Self-Assembly and Functional Applications of Bacterial Surface Layers

Bacterial surface layers, or S-layers, are highly ordered, two-dimensional protein lattices that envelop the cell envelope of many Gram-positive and Gram-negative species. These paracrystalline arrays form spontaneously through the intrinsic self-assembly of single or multiple surface-layer proteins into uniform lattices that serve as molecular sieves, protective barriers and scaffolds for the presentation of functional moieties. Advances in high-resolution imaging and biophysical analysis have elucidated the nucleation and growth of S-layer crystals on the lipopolysaccharide-rich outer membrane, revealing how membrane topology and ion binding regulate lattice formation. Functionally, S-layers contribute to cell shape maintenance, defence against environmental stress and mediating host–pathogen interactions. Exploiting their self-assembly and surface-display capabilities has given rise to novel applications in nanobiotechnology, including biosensors, vaccine platforms and bioinspired nanomaterials.

Research from Nature Portfolio

Recent studies have demonstrated that two-dimensional crystallisation is sufficient to construct and maintain a continuous S-layer in living cells. Using single-molecule tracking of surface-layer protein monomers on the outer membrane of a model bacterium, investigators have shown that randomly secreted monomers diffuse until they join the edges of growing lattice patches. Surface topography creates defects that guide crystal boundaries, ensuring coherent assembly around curved regions. This model unifies nucleation, growth and topological regulation of S-layer formation and suggests routes to harness biologically inspired protein crystals for programmable nanomaterials.

Self-Assembly and Functional Applications of Bacterial Surface Layers publication trend

The graph below shows the total number of articles in self-assembly and functional applications of bacterial surface layers across all publications each year (not limited to Nature Index journals).

Technical terms

S-layer: A crystalline sheet of protein subunits that self-assembles into a two-dimensional lattice on the surface of many bacteria and archaea.

Self-assembly: The spontaneous organisation of molecules into ordered structures through non-covalent interactions without external guidance.

Lipopolysaccharide (LPS): A complex glycolipid in the outer membrane of Gram-negative bacteria that anchors S-layer proteins and modulates assembly.

Two-dimensional protein lattice: A regular, repeating array of protein monomers in a single plane, often exhibiting hexagonal, square or oblique symmetry.

Cryo-electron microscopy (cryo-EM): A structural biology technique in which specimens are imaged at cryogenic temperatures to resolve macromolecular complexes at near-atomic resolution.

References

1. Microbial hauberks: composition and function of surface layer proteins in gammaproteobacterial methanotrophs. Applied and Environmental Microbiology (2024).
2. In Situ Structure of an Intact Lipopolysaccharide-Bound Bacterial Surface Layer. Cell (2019).
3. Electrochemical Biosensors Based on S-Layer Proteins. Sensors (2020).
4. Topologically-guided continuous protein crystallization controls bacterial surface layer self-assembly. Nature Communications (2019).