The impact of surface modification with fungal hydrophobins on microbial biofilm formation

Annika Rieder¹, Tatjana Ladnorg², Christof Wöll², Reinhard Fischer³, Ursula Obst¹, Thomas Schwartz^1*

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

* presenting author

The characteristics of a material and its corresponding surface properties are discussed to affect the biocompatibility and consequently bacterial adhesion. 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 protein coatings regarding hydrophobicity and homogeneity. 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. So far no significant differences in the biofilm formation on hydrophobin-coated versus uncoated surfaces were detected.

Recombinant hydrophobins could definitely be used for effective surface coating in monolayer manner. To stimulate the antibiofouling effect of the coating the hydrophobins need to be modified by e.g. antimicrobial peptides to influence the bacterial adhesion process.

Theme: Surface engineering and biofilm tribology