Retraction of entero pathogenic E. coli type IV pili promotes efficient host cell colonization, effector translocation and tight junction disruption

Type IV pili (Tfp) play a primary role in mediating the adherence of pathogenic bacteria to their hosts. The pilus filament can retract with an immense force. However, the role of this activity in microbial pathogenesis has not been rigorously explored. Experiments performed on volunteers suggested that the retraction capacity of entero pathogenic Escherichia coli (EPEC) Tfp is required for full virulence. Here we review our recent study1 in which we showed that the retraction capacity of the EPEC Tfp facilitates tight-junction disruption and actin-rich pedestal formation by promoting efficient bacterial protein effector translocation into epithelial host cells. We also present new data using live imaging confocal microscopy suggesting that EPEC adheres to mono layers in micro colonies and that Tfp retraction facilitates significant changes in the micro colony shape, which may be critical for efficient effector delivery. Our studies hence suggest novel insights into the role of pili retraction in EPEC pathogenesis.