title: The effects of cell sizes, environmental conditions, and growth phases on the strength of individual W303 yeast cells inside ESEM.
abstract: We performed in situ measurements of mechanical properties of individual W303 wild-type yeast cells by using an integrated environmental scanning electron microscope (ESEM)-nanomanipulator system. Compression experiments to penetrate the cell walls of single cells of different cell sizes (about 3-6 micro m diameter), environmental conditions (600 Pa and 3 mPa), and growth phases (early log, mid log, late log and saturation) were conducted. The compression experiments were performed inside ESEM, embedded with a 7 DOF nanomanipulator with a sharp pyramidal end effector and a cooling stage, i.e., a temperature controller. ESEM itself can control the chamber pressure. Data clearly show an increment in penetration force, i.e., 96 +/- 2, 124 +/- 10, 163 +/- 1, and 234 +/- 14 nN at 3, 4, 5, and 6 micro m cell diameters, respectively. Whereas, 20-fold increase in penetration forces was recorded at different environmental conditions for 5 micro m cell diameter, i.e., 163 +/- 1 nN and 2.95 +/- 0.23 mu N at 600 Pa (ESEM mode) and 3 mPa (HV mode), respectively. This was further confirmed from quantitative estimation of average cell rigidity through the Hertz model, i.e., ESEM mode (3.31 +/- 0.11 MPa) and HV mode (26.02 +/- 3.66 MPa) for 5 micro m cell diameter. Finally, the penetration forces at different cell growth phases also show the increment pattern from log (early, mid, and late) to saturation phases, i.e., 161 +/- 25, 216 +/- 15, 255 +/- 21, and 408 +/- 41 nN, respectively.
authors.affiliation: Department of Micro-Nano Systems Engineering, Nagoya University, Nagoya 464-8603, Japan. ridzuan@robo.mein.nagoya-u.ac.jp
authors.forename: Mohd Ridzuan
authors.initials: MR
authors.lastname: Ahmad
authors.forename: Masahiro
authors.initials: M
authors.lastname: Nakajima
authors.forename: Seiji
authors.initials: S
authors.lastname: Kojima
authors.forename: Michio
authors.initials: M
authors.lastname: Homma
authors.forename: Toshio
authors.initials: T
authors.lastname: Fukuda
mesh_terms: D018929:Cell Culture Techniques / Q000295:instrumentation / Q000379:methods*; D002455:Cell Division / Q000502:physiology; D049109:Cell Proliferation; D048429:Cell Size; D004548:Elasticity; D040542:Mechanotransduction, Cellular / Q000502:physiology*; D008846:Micromanipulation / Q000295:instrumentation / Q000379:methods*; D036103:Nanotechnology / Q000295:instrumentation / Q000379:methods*; D012441:Saccharomyces cerevisiae / Q000166:cytology* / Q000502:physiology*; D013045:Species Specificity; D013314:Stress, Mechanical