Related Experiment Video
Updated: Aug 11, 2026

Engineering Adherent Bacteria by Creating a Single Synthetic Curli Operon
Published on: November 16, 2012
Orientational control of fimE expression in Escherichia coli
B K Sohanpal1, H D Kulasekara, A Bonnen
1Research School of Biosciences, University of Kent, Canterbury, Kent, CT2 7NJ, UK.
Abstract:
Phase-variable expression of type 1 fimbriae is, in part, controlled by site-specific DNA inversion of the fim switch in Escherichia coli. Of the two fim recombinases (FimB and FimE) that catalyse the inversion reaction, FimE exhibits a strong bias for phase switching from the ON to the OFF orientation. The specificity associated with fimE is the result of two different mechanisms: (i) FimE exhibits a preference for the invertible element in the ON orientation as substrate for recombination; (ii) the invertible element in the OFF orientation acts in cis to inhibit recombinase activity (orientational control). We show here that the invertible element negatively regulates fimE, even though expression of a fimE-lacZYA transcriptional fusion is unaffected by orientational control. The fimE transcript extends into the invertible region and hence switch ON-specific and switch OFF-specific mRNA contain different sequences. Furthermore, we show that orientational control is suppressed by the insertion of a structured RNA (tRNA(Gly)) between fimE and the fim switch, indicating that the switch OFF-specific mRNA is inactivated by 3' to 5' degradation. Analysis of the fim switch reveals that it contains two inhibitory elements that exert orientational control independently.
Related Concept Videos
Directing Proteins to the Rough Endoplasmic Reticulum
Flagella and Motility in Bacteria
Coordination of Gene Expression Processes in Bacteria
Inducible Operons: lac Operon
Chemotaxis in E. coli
Stringent Response in E. coli

