Mechanism of Caulobacter adhesion

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DESCRIPTION (provided by applicant): The adhesion of bacteria to surfaces plays an important role in disease, providing the critical first step in the biofouling of a surface and in biofilm formation. The general goal of this research is to reach a detailed understanding of the mechanisms of bacterial adhesion, from the biophysics of adhesion to the coordination of the biosynthesis of cell surface structures that participate in this process. This project takes advantage of the bacterium Caulobacter crescentus, in which adhesive structures are synthesized in an ordered fashion at the same pole of the cell, making the study of adhesion more amenable than in most bacteria. Initial stages of adhesion involve flagellar motility and pili, and adhesion is cemented by synthesis of a polysaccharide holdfast. Pathogenic bacteria also use these adhesive structures, but their mechanism of action in adhesion is poorly understood. In addition, the adhesive force of individual Caulobacter cells is the strongest ever measured for a biological adhesive. This project has three major aims. The first aim will use highly synchronized cultures coupled to atomic force microscopy, fluorescence microscopy, and biophysical modeling to develop a detailed understanding of the various stages of adhesion. In particular, this aim will investigate a newly discovered surface contact-dependent trigger of adhesive polysaccharide export; this mechanism may also be used by pathogens. The second aim is to determine the function of holdfast polysaccharide synthesis and attachment proteins. Experiments are described to determine the biochemical function of these proteins and their contribution to adhesion. The third aim is to elucidate the mechanisms that control the timing and polar localization of holdfast synthesis. The effect of constitutively expressing holdfast synthesis proteins during the cell cycle on the timing of holdfast synthesis and adhesion will be determined. The localization of holdfast synthesis and attachment proteins and their interdependence for localization will be studied, and factors required for their localization will be identified. Bacterial adhesion, polysaccharide biosynthesis, and subcellular localization of proteins and virulence factors are essential components of bacterial pathogenesis. Insight gained from the study of this simple model system will be applicable to more complex bacterial pathogens and will enhance our ability to inhibit them.