Genetic modification of bacterial S-layer proteins to develop customized protein models for technical applications
In 1996 a group of scientists extracted soil samples of the uranium mining waste pile “Haberland“ near Johanngeorgenstadt to characterize bacterial populations and their living strategies within this heavy metal contaminated environment. Isolated Bacillus strains possessed one common characteristic: S-layer proteins, special envelope proteins, which cover the whole bacterial cell.
Previous studies of our group identified the ability of these proteins to differ selectively between toxic and useful metal ions. These proteins catch toxic heavy metal ions to protect the inner of their cells from toxic influences.
Beyond their selective metal bonding strategy S-layer proteins hold the ability to form 2D paracrystalline structures, which rearrange after isolation of proteins from bacterial cells. These characteristics make S-layer proteins interesting for applications like S-layer coated filter materials.
The use of proteins for applications require their cost-effective production. Therefore the development of efficient preparation methods are necessary. One way is the heterologous expression of the proteins in host organisms. With this method, protein yield is usually increased, protein quality is reproducible and production costs are lower.
Additionally this method facilitate the modification of the S-layer protein genes to create proteins with new characteristics.
Aim of this study is the production of special S-layer proteins with the help of heterologous expression. Surprisingly, the expression of special S-layer proteins modified the morphology of the host organism Escherichia coli from short fabaceous-shaped to long pipe-shaped cells. Parts of this study explore the background of these morphological changes and possible applications for this special structures.
S-layer proteins were fused to different proteins to analyse their presence and functional efficiency.
Several S-layer genes were assembled in the host organisms Escherichia coli and Lactococcus lactis to optimise conditions of cloning, expression and purification of S-layer proteins. Aim is the identification of an appropriate S-layer expression system.
Methods that are used include molecular biological methods such as PCR, gene cloning and expression and DNA-sequencing; fermentation, protein purification and infrared spectroscopy (IR) as well as several microscopic methods like light microscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM).
- Lederer, F. L., Günther, T. J., Flemming, K., Raff, J., Fahmy, K., Springer, A., Pollmann, K. (2010). Heterologous expression of the surface-layer-like protein SllB induces the formation of long filaments of Escherichia coli consisting of protein-stabilized outer membrane. Microbiology 156, 3584–3595.
- Lederer, F. L., Günther, T. J., Raff, J., Pollmann, K. (2011). E. coli filament formation induced by heterologous S-layer expression. Bioengineered bugs 2, 178–181.
- Lederer, F. L., Günther, T. J., Weinert, U., Raff, J., Pollmann, K. (2012). Development of bio-functionalized polyelectrolyte tubes using filamentous E. coli cells. In preparation.