ALBERT

Description: Microbial biofilms are an extremely successful way of life. Bacteria and fungi benefit in this symbiotic life form of metabolic exchange, protection and genetic flexibility. They produce a matrix of organic molecules in which they are embedded and which offers new habitats to other organisms, such as other bacteria or fungi. Biofilms cannot be avoided to colonize surfaces in unsterile habitats. So, they can be found everywhere in nature and in technical systems, but they play an ambivalent role. On the one hand biofilms are essential to degrade and transform water contaminations, but on the other hand they can diminish product qualities and damage capital equipment. Biofilms can cover medical equipment such as catheters and pathogenic bacteria, which may be living in the biofilms, are a continuous source of infection of the patients. In addition, the metabolism of the biofilm microorganisms may change the composition of the fluids or contaminate them with their products. As biofilms are all-round, the understanding of the biofilm formation and its manipulation are of prime importance in microbiology and material sciences. The choice of a material and the corresponding surface properties like mechanical properties, structure, polarity, and chemistry influence the binding of various molecules and cells. The surface properties affect the biocompatibility of a material and consequently also bacterial adhesion, and biofilm growth. In this project hydrophobins are used as a novel modification of surfaces to change surface properties like hydrophobicity and thus might have an effect on biofilm formation. Hydrophobins are fungal proteins, which selfassemble on hydrophobic as well as hydrophilic surfaces into extremely stable monolayers. Recombinant hydrophobins provide the opportunity to use these highly surface-active proteins for large-scale surface coatings. Hydrophobins are non-toxic and can be used for surface modification and functionalization (with e.g. enzymes) of industrial relevant materials like steel, plastics, and ceramics. In this project hydrophobin coated surfaces and their properties are studied with respect to bacterial cell adhesion, cell differentiation, and cellular growth with the aim to influence biofilm formation. In the first part of the project recombinant hydrophobins were produced and purified. Different surfaces were coated with hydrophobins and characterized, since the coating efficiency is the basis for subsequent biofilm formation studies. Biofilms were grown on natural as well as hydrophobin coated surfaces and different methods were established to analyse biofilm formation. Since the hydrophobin coated surfaces did not reduce microbial growth, we designed modified fusion hydrophobins and attached cationic antimicrobial peptides (AMPs) to the hydrophobins.