MSc Thesis Presentation: Quantitative, Biologically-Motivated, Computational Model for the Twitching Motility of Pseudomonas aeruginosa

MSc Thesis Presentation

Candidate: James Howard

Abstract

The bacterium Pseudomonas aeruginosa uses thin protein filaments called type IV pili (T4P) to pull itself across a surface in a motion known as twitching motility. To examine the quantitative plausibility of this mechanism, we developed a detailed computational model of pilus action that employs biological and mechanical parameters measured from observations of P. aeruginosa motility. A key parameter is the persistence length of T4P, which characterizes the T4P flexibility. Measurements of the T4P persistence length have observed either ~1 μm or ~1 nm, depending on the method of observation. Our model reconciles these values and supports the idea that the filament experiences a conformational change when the pilus is under tension, enhancing filament flexibility. Also, some high velocity events were observed due to the sudden release of elastic potential energy when at least two pili are pulling in opposing directions and one of the pili de-adheres from the surface.

Examination Committee:

• Dr. Martin Williams, Chair
• Dr. Robert Wickham, Advisor
• Dr. Michael Massa
• Dr. Hendrick de Haan, External Examiner