Nanoscale characterization and determination of adhesion forces of Pseudomonas aeruginosa pili by using atomic force microscopy
== Context Type IV pili (Tfp) are filamentous organelles used by many species of bacteria to adhere to and move about a surface. Tfp are located at one pole of the bacterium, and can attach using both specific and non-specific adhesion mechanisms to anchor the bacterium to the surface. Bacteria also pull their Tfp back into the cell wall and dissasemble its pilin subunits, thereby shortening the pilus and generating a retraction force. This retraction force is used to pull the bacterium along the surface, called twitching motility. As Tfp are crucial for the formation of biofilms in many bacteria species, understanding their mechanical properties has become an important line of study. This experiment studied P. aeruginosa Tfp using AFM techinques.
Experiment and Results
Bacteria were attached to an AFM canitlever tip. The tip was then brought near a surface (made of mica) until it just touched the surface. Presumably, this allowed the bacteria, which were sitting on the side of the tip, to extend a pilus and attach to the surface. The tip was then displaced upwards, and the amount of force necessary to keep the tip at each displacement was recorded. This generated force-versus-displacement curves, giving information about the adhesion forces of the Tfp.