Berlin 2008 – scientific programme

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BP: Fachverband Biologische Physik

BP 12: Cellular Force Generation

BP 12.1: Talk

Tuesday, February 26, 2008, 17:30–17:45, C 243

Force and Motorprotein Concentration Determine Dynamics of Bacterial Pili — •Martin Clausen and Berenike Maier — WWU Münster, Institut für Allgemeine Zoologie und Genetik, Schloßplatz 5, 48149 Münster, Germany

Type IV pili are major bacterial virulence factors required for adhesion, surface motility and gene transfer. In the human pathogen Neisseria gonorrhoeae, these flexible polymeric filaments extend several micrometers from the cell surface and generate force in the range of 100pN by retraction. Two antagonistic ATPases, PilF and PilT, support elongation and retraction respectively. We investigated the dynamics of individual pili using laser tweezers and observed that the probability for polymerization increased with increasing force for forces up to 100pN. The length change of the pilus as a function of time was analyzed using the statistical randomness parameter as well as direct sectioning. The data reveals two distinct time scales: on a time scale of miliseconds backsteps and pauses were detected, while on the longer timescale directional reversal of the pilus movement was observed. This observation is inconsistent with simple Arrhenius kinetics. We therefore investigated the effect of the concentration of the pilus retraction ATPase PilT and found that the retraction probability decreased with decreasing PilT concentration indicating that binding of PilT strongly increases the retraction probability. Fine-tuning of pilus dynamics by force and motor concentration may be important for surface motility and interaction with mammalian cells.