Measuring the bending stiffness of bacterial cells using an optical trap. Author Siyuan Wang, Hugo Arellano-Santoyo, Peter Combs, Joshua Shaevitz Publication Year 2010 Type Journal Article Abstract We developed a protocol to measure the bending rigidity of filamentous rod-shaped bacteria. Forces are applied with an optical trap, a microscopic three-dimensional spring made of light that is formed when a high-intensity laser beam is focused to a very small spot by a microscope's objective lens. To bend a cell, we first bind live bacteria to a chemically-treated coverslip. As these cells grow, the middle of the cells remains bound to the coverslip but the growing ends are free of this restraint. By inducing filamentous growth with the drug cephalexin, we are able to identify cells in which one end of the cell was stuck to the surface while the other end remained unattached and susceptible to bending forces. A bending force is then applied with an optical trap by binding a polylysine-coated bead to the tip of a growing cell. Both the force and the displacement of the bead are recorded and the bending stiffness of the cell is the slope of this relationship. Keywords Escherichia coli, Bacteriological Techniques, Cephalexin, Optical Tweezers, Polylysine Journal J Vis Exp Issue 38 Alternate Journal J Vis Exp Google ScholarBibTeXEndNote X3 XML