Structure-function relationship in bacterial adhesins

was focused on the structure and evolution of bacterial adhesins from various adhesin families, we noticed that there is a lack of knowledge on the molecular mechanisms underlying adhesion. Only few adhesins have been characterized in detail, and frequently, the exact binding sites for host molecules, or the sites mediating attachment to abiotic surfaces, are unknown. Moreover, the exact mechanisms of how adhesins reach the bacterial cell surface to fulfil their function are not understood well. Both processes, the adhesion as such, but also the biogenesis of adhesins, are highly relevant for drug discovery: small-molecule inhibitors could block adhesion and biofilm formation e.g. on medical implants, and drugs that would inhibit the formation of adhesive structures could be effective novel antimicrobial compounds. The aim of this project is to obtain a better understanding of individual adhesins and of their binding modes, and of their biogenesis. The ultimate goal of this research is the development of antimicrobial compounds, i.e. direct or indirect inhibitors of bacterial adhesion. In order to identify novel antimicrobial compounds we are developing assays in our labs that will allow us to screen for molecules with the desired functionality. Subsequently we will transfer our developed assay to the High-Throughput Chemical Biology Screening Platform, located at the Biotechnology Center in Oslo. There, we are aiming to set up the necessary pilot screen that will lead us to a target based screen against a diversity library containing at least 28500 compounds. After a verification process, the successful candidates will be used to expand on the understanding of adhesion structure and function. As an alternative approach, individual adhesive domains and their binding partners are being investigated using structural methods. Successful trials will lead to greater understanding of the structure-function relationship of the adhesive domains and form a foundation for further structure guided drug discovery and design. Results from these trials can also be combined with the screening development described above.

We have achieved all milestones of the project - and have found lead molecules that inhibit bacterial adhesion. We hope to now be able to develop those further into drugs or research tools in other, more applied-science grants/grant applications. Within the grant period, we have established new collaborations with researchers in Germany and the UK (and more recently, China), that have already led to several successful grants (including a DAAD/NFR grant for establishing new collaborations with Germany, a Marie Curie International Training Network, and participation in a COST action).

Adhesion of bacteria to surfaces is essential for many aspects of microbial life: surface recognition and attachment, biofilm formation, and pathogenesis. Adhesion to host tissues is frequently among the first steps in host colonization by pathogens. Adhesion in pathogens is mediated by usually proteinaceous adhesins, or by carbohydrate polymers, and the array of adhesins expressed on the bacterial cell surface affects the virulence, persistence and host specificity of the organism. In recent projects, where our research was focused on the structure and evolution of bacterial adhesins from various adhesin families, we noticed that there is a lack of knowledge on the molecular mechanisms underlying adhesion. Only few adhesin domains have been characterized in detail, and frequently, the exact binding sites for host molecules, or the sites mediating attachment to abiotic surfaces, are unknown. Moreover, the exact mechanisms of how adhesins reach the bacterial cell surface to fulfill their function are not understood well. Both processes, the adhesion as such, but also the biogenesis of adhesins, are highly relevant for drug discovery: small-molecule inhibitors could block adhesion and biofilm formation e.g. on medical implants, and drugs that would inhibit the formation of adhesive structures could be effective novel antimicrobial compounds. The aim of this project is to obtain a better understanding of individual adhesin domains and of their binding modes, and of the transport and protein folding processes necessary for their biogenesis, using trimeric autotransporter adhesins as a model system. The ultimate goal of this research is the development of antimicrobial compounds. We intend to develop suitable assays for high-throughput screening, based on the results on adhesion and biogenesis. These plate-based assays will then be used in a chemical biology screening facility to identify lead compounds, i.e. direct or indirect inhibitors of adhesion.