Characterization of the nanomechanical properties of the fission yeast (Schizosaccharomyces pombe) cell surface by atomic force microscopy

Abstract

Variations in cell wall composition and biomechanical properties can contribute to the cellular plasticity required during complex processes such as polarized growth and elongation in microbial cells. This study utilizes atomic force microscopy (AFM) to map the cell surface topography of fission yeast, Schizosaccharomyces pombe, at the pole regions and to characterize the biophysical properties within these regions under physiological, hydrated conditions. High‐resolution images acquired from AFM topographic scanning reveal decreased surface roughness at the cell poles. Force extension curves acquired by nanoindentation probing with AFM cantilever tips under low applied force revealed increased cell wall deformation and decreased cellular stiffness (cellular spring constant) at cell poles (17 ± 4 mN/m) relative to the main body of the cell that is not undergoing growth and expansion (44 ± 10 mN/m). These findings suggest that the increased deformation and decreased stiffness at regions of polarized growth at fission yeast cell poles provide the plasticity necessary for cellular extension. This study provides a direct biophysical characterization of the S. pombe cell surface by AFM, and it provides a foundation for future investigation of how the surface topography and local nanomechanical properties vary during different cellular processes.

Fission yeast polycystin Pkd2p promotes cell size expansion and antagonizes the Hippo-related SIN pathway

“…The spring constant of wild-type cells was 42±10 mN m −1 (mean±s.d. ), which is consistent with previously reported values (Gibbs et al, 2021). In comparison, the spring constants of pkd2-B42 and pkd2-81KD mutant cells were 40% lower at the permissive temperature (26±12 mN m −1 and 27±9 mN m −1 , respectively) (Fig.…”

“…We modeled the turgor pressure based on the experimentally determined force curves and spring constants. Consistent with previous estimates (Abenza et al, 2015;Atilgan et al, 2015;Davi et al, 2018;Gibbs et al, 2021;Minc et al, 2009), our calculation determined a Young's modulus of 1.3±0.4 MPa (mean±s.d.) for the wild-type cells (Table S2).…”

“…Turgor pressure of pkd2-B42 mutant cells Like other walled cells, fission yeast cells depend on turgor pressure, which results from higher intracellular osmolarity than the environment, to expand. As an indirect measurement of the turgor of the pkd2-B42 mutant, we quantified its stiffness using AFM based on a method that we recently established (Gibbs et al, 2021) (Fig. 4A,B).…”

“…To estimate the decrease in the turgor pressure of pkd2 mutant cells, we applied the Hertz model (see Eqn 2 in Materials and Methods) to obtain their Young's moduli. AFM indentation analysis has been used previously to calculate the Young's modulus of cellular elasticity and turgor pressure for microbial cells (Arfsten et al, 2010;Gibbs et al, 2021). We modeled the turgor pressure based on the experimentally determined force curves and spring constants.…”

“…Data processing was performed through MFP-3D software in Igor Pro to obtain curve fits and spring constants. AFM extension force indentation curves were used to calculate Young's elasticity moduli by the Asylum Igor Pro MFP-03D software (WaveMetrics, USA), using the Hertz modeling equation as previously described (Gibbs et al, 2021):…”