The bacterial adhesive protein, FimH, is the most common adhesin of Escherichia coli and
mediates weak adhesion at low flow but strong adhesion at high flow. There is evidence that
this occurs because FimH forms catch bonds, defined as bonds that are strengthened by
tensile mechanical force. Here, we applied force to single isolated FimH bonds with an
atomic force microscope in order to test this directly. If force was loaded slowly, most of the
bonds broke up at low force (< 60 piconewtons of rupture force). However, when force was …