Adsorption kinetics of cell wall components of gram positive bacteria on technical surfaces studied by QCM-D

In general, the cell wall components of gram-positive bacteria e.g. single lipid bilayer, peptidoglycan, Surface-layer proteins (S-layer) and other biopolymers are well studied. These cell wall components are interesting for several bio-induced technical applications such as biosorptive materials. Although biosorption processes have been intensively investigated, the investigation of metal interaction with biomolecules as well as adsorption processes on substrates on molecular level remains challenging.
In our work we used the quartz crystal microbalance with dissipation monitoring (QCM-D) in order to study the layer formation of cell wall compounds and interaction processes on the nano scale range.
This analytical method allows the detailed detection of array formation of bacterial S-layer proteins and gives a better understanding of the self-assembling processes. S-layer proteins as a part of the outer cell envelope of many eubacteria and archaea form paracrystalline protein lattices in strain depended geometrical structures [1]. Once isolated the proteins exhibit the ability to form these lattices on different kinds of interfaces and possesses equal to the bacteria cells high metal binding capacities. These properties open a wide spectrum of applications e.g. ultrafiltration membranes for organic and inorganic ions and molecules, templates for the synthesis of catalytic nanoparticles and other bio-engineered materials [2, 3].
By performing different experiments with and without modification of technical surfaces with adhesive promoters e.g. polyelectrolytes it is possible to make exact statements regarding coating kinetics, layer stability and interaction with metals. Subsequent atomic force microscopy (AFM) studies enable the imaging of bio nanostructures and reveal complex information of structural properties. Aim of these investigations is the assembly of a simplified biological multilayer based on cell compounds of gram positive bacteria in order to clarify sorption processes in a complex system. The understanding of coating, biological and biological-metal interaction processes is interesting for different technical applications.

1. U.B. Sleytr et al., Prog. Surf. Sci. 68 (2001), 231-278.
2. K. Pollmann et al., Biotechnology Advances 24 (2006), 58– 68.
3. J. Raff et al., Chem. Mater. 15 (2003), 240-244.