THE INFLUENCE OF HYDROPHOBIN-COATED SURFACES ON MICROBIAL BIOFILM FORMATION

Annika Rieder¹, Tatjana Ladnorg², Christof Wöll², Reinhard Fischer³, Ursula Obst¹, Thomas Schwartz¹

¹ Karlsruhe Institute of Technology, Institute of Functional Interfaces, Department of Interface Microbiology, P.O. Box 3640, 76021 Karlsruhe, Germany

² Karlsruhe Institute of Technology, Institute of Functional Interfaces, Department of Surface Chemistry, P.O. Box 3640, 76021 Karlsruhe, Germany

³ Karlsruhe Institute of Technology, Institute for Applied Biosciences, Department of Microbiology, Hertzstr. 16, 76187 Karlsruhe, Germany

Biofilms cannot be avoided on a great variety of natural and synthetic surfaces in unsterile habitats. However the characteristics of the material and its corresponding surface properties affect the biocompatibility and consequently bacterial adhesion and biofilm growth.

In this approach hydrophobins are used as a novel modification of materials to change the surface properties and thus to influence microbial biofilm formation. Hydrophobins are non-toxic fungal proteins which self-assemble on different surfaces into extremely stable monolayers in an amphiphilic manner. Recombinant hydrophobins provide the opportunity to use these highly surface-active proteins for large-scale surface modification and functionalization (with e.g. enzymes) of industrial and medical relevant materials.

Thus, hydrophobin coating protocols were developed for different materials. Quartz crystal microbalance measurements were used to analyse the adsorption behaviour and contact angle measurements, immunofluorescent labellings and atomic force microscopy were applied to characterize the properties of the protein coatings. The recombinant hydrophobins self-assembled on the surfaces depending on different parameters such as incubation temperature or incubation time.

The growth behaviour of various microorganisms was studied on hydrophobin modified versus unmodified surfaces. Single bacteria strains as well as natural bacterial communities were used to analyse biofilm formation. Apart from conventional plating experiments, fluorescent microscopy and molecular-biological methods such as denaturing gradient gel electrophoresis were applied to determine differences in the biofilm growth.

Recombinant hydrophobins are well suited for surface modification and functionalization. To enhance the effects on the biofilm growth further modifications of the recombinant hydrophobins are necessary by e.g. antimicrobial peptides.