Mechanical double layer model for Saccharomyces cerevisiae cell wall.

Area of Science:

• * Biophysics
• * Materials Science
• * Microbiology

Background:

• * Atomic force microscopy (AFM) and micromanipulation yield disparate elastic moduli for Saccharomyces cerevisiae cell walls.
• * Existing models like Hertz-Sneddon and Reissner solutions are inadequate for yeast's thick, layered cell walls.

Purpose of the Study:

• * To develop a model explaining the discrepancy in yeast cell wall stiffness measurements.
• * To determine the mechanical properties of the inner and outer layers of the yeast cell wall.

Main Methods:

• * Finite element modeling (FEM) was employed to analyze mechanical responses.
• * A double-layer cell wall model was proposed, comprising a soft outer layer (mannoproteins) and a stiff inner layer (β-glucan and chitin).

Main Results:

• * Hertz-Sneddon analysis is inappropriate for AFM indentation of single-layer core-shell structures.
• * The Reissner solution is unsuitable for thick-walled yeast cells.
• * The double-layer model successfully explains measurements across different length scales.
• * AFM provides estimates for the outer layer's modulus, while micromanipulation yields total cell wall stiffness.

Conclusions:

• * AFM and micromanipulation measure different aspects of yeast cell wall mechanics.
• * The proposed double-layer model accurately represents the yeast cell wall structure.
• * Combining data from AFM and micromanipulation allows for estimation of the inner stiff layer's mechanical properties.