NUCLEATOR-DEPENDENT INTERCELLULAR ASSEMBLY OF ADHESIVE CURLI ORGANELLES IN ESCHERICHIA-COLI

Bacterial adhesion to other bacteria, to eukaryotic cells, and to extr acellular matrix proteins is frequently mediated by cell surface-assoc iated polymers (fimbriae) consisting of one or more subunit proteins. We have found that polymerization of curlin to fimbriae-like structure s (curli) on the surface of Escherichia coli markedly differs from the prevailing model for fimbrial assembly in that it occurs extracellula rly through a self-assembly process depending on a specific nucleator protein. The cell surface-bound nucleator primes the polymerization of curlin secreted by the nucleator-presenting cell or by adjacent cells . The addition of monomers to the growing filament seems to be driven by mass action and guided only by the diffusion gradient between the s ource of secreted monomer and the surface of monomer condensation.