Kinetics of phase variation between S and type-1 fimbriae of Escherichia coli

Abstract The rate of fimbrial phase variation in Escherichia coli strain 3040 was determined. The strain has type-1 and S fimbriae. The bacterial culture was fractionated into homogeneous subpopulations expressing either one of the fimbrial types only; the subpopulations were inoculated into broth and the fimbriation of individual cells was assayed by immunofluorescence as a function of time. The rate of the shift from S- or type-1-fimbriate cells to non-fimbriate ones was of the order of 10⁻² per cell generation and more rapid than a direct shift from one fimbrial phase to another, although both types of phase variations were observed.