Spatially resolved force spectroscopy of bacterial surfaces using force-volume imaging

Area of Science:

• Microbial cell surface analysis
• Atomic Force Microscopy (AFM) applications
• Biophysical characterization

Background:

• Atomic force microscopy (AFM) is crucial for measuring forces at microbial cell surfaces.
• Contact-mode AFM imaging is typically used to locate measurement points but can distort cell topography.
• Bacterial cell deformability and curvature complicate accurate imaging with contact-mode AFM.

Purpose of the Study:

• To compare AFM force-volume mode imaging with contact-mode imaging for bacterial cells.
• To demonstrate the artifact introduced by contact-mode imaging due to cell deformation.
• To highlight the advantages of force-volume mode for accurate topographic reconstruction and mechanical property extraction.

Main Methods:

• Imaging the bacterial cell Shewanella putrefaciens using AFM in both contact mode and force-volume mode.
• Analyzing the topographic data obtained from both imaging modes to identify discrepancies.
• Acquiring force-indentation data using force-volume mode for mechanical property analysis.

Main Results:

• Contact-mode imaging deforms bacterial cells, inaccurately locating the apical surface and periphery.
• Force-volume mode imaging reconstructs topography from individual force profiles, avoiding deformation artifacts.
• Force-volume measurements provide load-indentation data for extracting mechanical properties like Young's modulus and turgor pressure.

Conclusions:

• Force-volume mode AFM is superior to contact mode for accurate imaging of bacterial cell surfaces.
• The avoidance of deformation artifacts in force-volume mode enables reliable topographic mapping.
• Force-volume mode AFM facilitates comprehensive mechanical characterization of microbial cells.