Monitoring the osmotic response of single yeast cells through force measurement in the environmental scanning electron microscope

Measurement Science and Technology Volume 25 Number 2, 2014.

Anna Jansson¹, Alexandra Nafari^2,3, Kristina Hedfalk⁴, Eva Olsson¹, Krister Svensson⁵ , Anke Sanz-Velasco³

 

¹ Department of Applied Physics, Chalmers University of Technology, SE-41296 Gothenburg, Sweden  and
² Nanofactory Instruments AB, SE-41288 Gothenburg, Sweden and
³ Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-41296 Gothenburg, Sweden and
⁴ Department of Chemistry and Molecular Biology, University of Gothenburg, SE-40530 Gothenburg, Sweden and
⁵ Department of Physics and Electrical Engineering, Karlstad University, SE-65188 Karlstad, Sweden.

 

Abstract

 We present a measurement system that combines an environmental scanning electron microscope (ESEM) and an atomic force microscope (AFM). This combination enables studies of static and dynamic mechanical properties of hydrated specimens, such as individual living cells. The integrated AFM sensor provides direct and continuous force measurement based on piezoresistive force transduction, allowing the recording of events in the millisecond range. The in situ ESEM-AFM setup was used to study Pichia pastoris wild-type yeast cells. For the first time, a quantified measure of the osmotic response of an individual yeast cell inside an ESEM is presented. With this technique, cell size changes due to humidity variations can be monitored with nanometre accuracy. In addition, mechanical properties were extracted from load–displacement curves. A Young’s modulus of 13–15 MPa was obtained for the P. pastoris yeast cells. The developed method is highly interesting as a complementary tool for the screening of drugs directed towards cellular water transport activity and provides new possibilities of studying mechanosensitive regulation of aquaporins.

Go To Journal