| AVS 64th International Symposium & Exhibition | |
| Biomaterial Interfaces Division | Thursday Sessions |
| Session BI+AS+SA-ThM |
| Session: | Characterisation of Biological and Biomaterial Surfaces |
| Presenter: | Christine Müller-Renno, University of Kaiserslautern, Department of Physics and Research Center Optimas, Germany |
| Authors: | N. Davoudi, University of Kaiserslautern, Department of Physics and Research Center Optimas, Germany K. Huttenlochner, University of Kaiserslautern, Department of Physics and Research Center Optimas, Germany C. Schlegel, University of Kaiserslautern, Institute of Bioprocess Engineering, Germany M. Huster, University of Kaiserslautern, Institute of Bioprocess Engineering, Germany C. Müller-Renno, University of Kaiserslautern, Department of Physics and Research Center Optimas, Germany R. Ulber, University of Kaiserslautern, Institute of Bioprocess Engineering, Germany C. Ziegler, University of Kaiserslautern, Department of Physics and Research Center Optimas, Germany, Germany |
| Correspondent: | Click to Email |
Biofilms are often unwanted, but can also be utilized in biofilm reactors. In such a reactor different forces act on the cells: lateral forces by flow, forces perpendicular to the interface which dominate the first contact and the biofilm formation, and forces on the cell-wall by turgor pressure which influence the viability of the cells. The interplay of these forces plays a major role in the establishment of a biofilm.
Here, we report on the seawater bacterium Paracoccus seriniphilus on titanium and glass. Microstructured titanium is our substrate of choice in the reactor. We hence have to understand the influence of wettability, roughness, defined structures, and environmental conditions such as pH and ionic strength on the viability as well as the bacterial attachment and detachment.
In a first set of experiments, the turgor pressure of the bacteria was determined as a function of pH and salinity by measuring force-distance curves with a scanning force microscope (SFM). As a seawater bacterium, P. seriniphilus can easily adapt to saline conditions and can survive at NaCl concentrations up to 100 gL-1. Depending on the ionic strength the turgor pressure and thus the elasticity and size of the cell changes. P. seriniphilus has its optimum pH at 7, but at pH 4 the results point to an active adaption mechanism to acidic conditions. The results at pH 11 show that P. seriniphilus cannot adapt to alkaline conditions.
As next step the vertical adhesion forces of a single bacterium were measured as a function of pH, ionic strength, and substrate. The adhesion force of one single cell decreases from pH 4 to pH 9. As a function of the ionic strength, the adhesion forces increase with increasing salt concentration with a pronounced spike (higher adhesion forces) at 0.9 % NaCl. All adhesion force changes completely correlate with the electrostatics as determined by zetapotential measurements. A conditioning film of growth medium strongly decreases the attachment forces. Thus the first bacterial layer should grow without medium at pH 4.
In a last step, the lateral detachment forces of the bacteria were measured. There is a clear correlation between the applied force and the number of moved bacteria, but the detachment forces vary for the individual bacteria. For small lateral forces (0.5 nN), the wettability of the substrate seems to control the detachment process. For higher lateral forces (2-3 nN), the effect of the wettability gets lost and the roughness of the samples controls the cell detachment. These detachment forces are in the same range or higher than the shear forces applied by the fluid flow.