The proposed research focuses on the structural and functional organization of the cell surface of Escherichia coli and Salmonella anatum; special emphasis is placed on the characterization of the macromolecular structure and composition of export domains of the envelope membranes and on the sites at which specific interactions occur between invading macromolecules (virus capsids, colicin) and the host cell surface. We propose a model of the bacterial surface in which growth-related functions are clustered in discrete domains. These functional clusters coincide with the structural mosaic formed by the zones of adhesion between outer and inner membrane. At these """"""""adhesion sites,"""""""" newly synthesized lipopolysaccharides, capsular polysaccharides and membrane proteins are exported; also enzyme and receptor activities are localized at these sites. Furthermore, adhesion areas serve as injection sites for a large variety of bacteriophages. We propose to study a) the ultra-structure and the formation of adhesion sites in relation to cell growth, and to bacteriophage and colicin interactions; b) the localization of sites of production and transmembrane traffic involving polysaccharides and outer membrane proteins; c) procedures to isolate, concentrate, and analyse membrane adhesion sites. These projects will utilize new ultrastructural approaches in combination with immunological, virological and biochemical techniques. We expect that the proposed research will increase our understanding of 1) the structure, assembly and function of the surface of microbial cells; 2) the location of the machinery for assembly and export of polysaccharides and proteins; and 3) the functional clusters which incorporate the great variety of virus receptors and also represent the sites at which membrane components are inserted into the growing cell surface. In addition, we anticipate that the advances in the proposed methodology will be of benefit to a broad area of cell biology.
