Dependence of the initial adhesion of biofilm forming Pseudomonas putida mt2 on physico-chemical material properties

Bacterial adhesion is strongly dependent on the physico-chemical properties of materials and plays a fundamental role in the development of a growing biofilm. Selected materials were characterized with respect to their physicochemical surface properties. The different materials, glass and several polymer foils, showed a stepwise range of surface tensions (gamma(s)) between 10.3 and 44.7 mN m(-1). Measured zeta potential values were in the range between-74.8 and -28.3 mV. The initial bacterial adhesion parameter q(max) was found to vary between 6.6 x 10(6) and 28.1 x 10(6) cm(-2). By correlation of the initial adhesions kinetic parameters with the surface tension data, the optimal conditions for the immobilization of Pseudomonas putida mt2 were found to be at a surface tension of 24.7 mN m(-1). Both higher and lower surface tensions lead to a smaller number of adherent cells per unit surface area. Higher energy surfaces, commonly termed hydrophilic, could constrain bacterial adhesion because of their more highly ordered water structure (exclusion zone) close to the surface. At low energy surfaces, commonly referred to as hydrophobic, cell adhesion is inhibited due to a thin, less dense zone (depletion layer or clathrate structure) close to the surface. Correlation of qmax with zeta potential results in a linear relationship. Since P. putida carries weak negative charges, a measurable repulsive effect can be assumed on negative surfaces.