Type 1 Fimbriae of Escherichia coli

During the last few decades a number of aspects related to the molecular biology of type 1 fimbriae of Escherichia coli have been investigated using a variety of approaches, including classical serology and immunology, molecular genetics, and cell biology. Type 1 fimbriae are characterized by their ability to mediate agglutination of guinea pig erythrocytes in the absence of α-D-mannose but not in its presence. Fimbriae consisting of all the structural components, i.e., FimA, FimF, FimG, and FimH, were observed to be much more prone to breakage and depolymerization than pure FimA fimbriae. Biochemical analysis of fimbriae subsequently revealed that minor components were indeed integral parts of the organelles. The molecular system underlying the phase variation system of type 1 fimbriae seems to be a unique feature and is not found in other systems controlling fimbrial expression. The nature of the type 1-fimbrial receptors has not only been studied utilizing erythrocytes but also using epithelial cells of different origins.