MSc Thesis Presentation: Nanomechanical Measurements of Viscoelastic Properties of Bacterial Cells: Effect of Antimicrobial Peptides and Challenges Associated with Measurements in Buffer

MSc Thesis Presentation

Candidate: Richard Parg

Abstract

The effectiveness of antimicrobial compounds can be easily screened; however, their mechanism of action is much more difficult to determine. Many compounds act by compromising the mechanical integrity of the bacterial cell, and we have developed an atomic force microscopy (AFM)-based creep-deformation technique to evaluate changes in the time dependent mechanical properties of bacterial cells upon exposure to antimicrobials. Measurements revealed large changes to the viscoelastic parameters including a distinctive signature for the loss of integrity of the bacterial cell envelope. This technique provides unique insight into the kinetics and action of antimicrobials on bacteria. Initial experiments focused on Pseudomonas aeruginosa PAO1 bacterial cells in Milli-Q water, for which the cells can withstand large osmotic pressures. Our subsequent experiments addressed the challenges of performing AFM creep deformation experiments on live cells in PBS buffer. We describe measurements of, and improvements to, the stability of the experimental set-up in an effort to facilitate these challenging experiments.

Examination Committee:

Dr. Hermann Eberl (Department of Mathematics and Statistics), Chair 

Dr. John Dutcher (Department of Physics), Advisory Committee

Dr. Leonid Brown (Department of Physics), Examination Committee