Quantification of the lateral detachment force for bacterial cells using atomic force microscope and centrifugation

Area of Science:

• Microbiology
• Biophysics
• Materials Science

Background:

• Understanding bacterial adhesion forces is crucial for controlling biofilm formation and microbial contamination.
• Existing methods for measuring bacterial detachment force have limitations in precision and applicability.

Purpose of the Study:

• To develop and optimize a quantitative atomic force microscope (AFM) method for measuring the lateral detachment force of individual bacterial cells.
• To evaluate key parameters including scan size, scan rate, and cantilever selection for accurate force measurements.

Main Methods:

• Utilized the contact mode of AFM to probe and quantify the lateral forces required to detach individual bacterial cells.
• Optimized scan size to 40x40 μm² for sufficient cell capture and identification.
• Optimized scan rate to 40 μm/s for a balance of accuracy and efficiency, and developed a protocol for selecting cantilevers based on spring constant.

Main Results:

• Determined the lateral detachment force for Escherichia coli cells on stainless steel (0.763±0.167 nN) and poly-l-lysine coated glass (0.639±0.136 nN).
• Demonstrated good repeatability and sensitivity of the AFM method across different bacteria-substrate combinations.
• AFM-derived detachment force values were comparable to those obtained by centrifugation.

Conclusions:

• The developed AFM-based method provides a reliable and sensitive approach for quantifying bacterial lateral detachment forces.
• The optimized protocol allows for accurate assessment of bacterial adhesion, aiding in the development of anti-adhesion strategies.