F1C fimbriae of a uropathogenic Escherichia coli strain: Genetic and functional organization of the foc gene cluster and identification of minor subunits

The genetic organization of the foc gene cluster has been studied; six genes involved in the biogenesis of F1C fimbriae were identified. focA encodes the major fimbrial subunit, focC encodes a product that is indispensable for fimbria formation, focG and focH encode fimbrial subunits, and focI encodes a protein which shows at least two minor subunits, FocG and FocH. Minor proteins of similar size were observed in purified S fimrbiae. Remarkably, some mutations in the foc gene cluster result in an altered fimbrial morphology, i.e., rigid stubs or long, curly fimbriae.