A Comprehensive View of Type IV Pilus Retraction Forces across the Bacterial Domain

Abstract

Type IV pili are long flexible polymeric appendages emanating from many bacteria. They are playing key roles in many bacterial functions: DNA uptake, motility, colonization, infection, biofilm formation, aggregation. A central feature of these appendages is their ability to undergo cycles of elongation and retraction enabling them to exert physical forces on their surroundings. In order to gain insight in the differences and commonalities of the biophysical characteristics of those retraction forces across evolution, we have measured, combining different techniques, the retraction forces of type IV pili in a wide range of bacterial genus (Neisseria, Escherichia, Vibrio, Synechocystis, Streptococcus). Of particular interest is the role that the so-called retraction ATPase (pilT) plays in the biophysical characteristics of the retraction forces. The direct comparison of the retraction forces in different mutants of those very different genus will help ascertain the common biophysical features of the Type IV pilus machinery across bacteria.