Techniques to measure pilus retraction forces

The importance of physical forces in biology is becoming more appreciated. Neisseria gonorrhoeae has become a paradigm for the study of physical forces in the bacterial world. Cycles of elongations and retractions of Type IV pili enables N. gonorrhoeae bacteria to exert forces on its environment, forces that play major roles in the life cycle of this pathogen. In order to better understand the role of these forces, there is a need to fully characterize them. Here, we present two different techniques, optical tweezers and Polyacrylamide MicroPillars (PoMPs), for measuring pilus retraction forces. Initially designed for N. gonorrhoeae, these assays can be readily modified to study other pilus-bearing bacteria including Neisseria meningitidis.