The mechanical properties of Saccharomyces cerevisiae

Cell-wall mechanical properties play an integral part in the growth and for m of Saccharomyces cerevisiae, In contrast to the tremendous knowledge on t he genetics of S. cerevisiae, almost nothing is known about its mechanical properties. We have developed a micromanipulation technique to measure the force required to burst single cells and have recently established a mathem atical model to extract the mechanical properties of the cell wall from suc h data, Here we determine the average surface modulus of the S, cerevisiae cell wall to be 11.1 +/- 0.6 N/m and 12.9 +/- 0.7 N/m in exponential and st ationary phases, respectively, giving corresponding Young's moduli of 112 /- 6 MPa and 107 +/- 6 MPa, This result demonstrates that yeast cell popula tions strengthen as they enter stationary phase by increasing wall thicknes s and hence the surface modulus, without altering the average elastic prope rties of the cell-wall material. We also determined the average breaking st rain of the cell wall to be 82% +/- 3% in exponential phase and 80% +/- 3% in stationary phase, This finding provides a failure criterion that can be used to predict when applied stresses (e,g,, because of fluid flow) will le ad to wall rupture, This work analyzes yeast compression experiments in dif ferent growth phases by using engineering methodology.