Detecting Bacterial Surface Organelles on Single Cells Using Optical Tweezers

Area of Science:

• Microbiology
• Biophysics
• Cell Biology

Background:

• Bacterial surface organelles, like adhesion pili, are crucial for intercellular communication, motility, and adhesion.
• Gram-negative bacteria use adhesion pili for attachment to host cells, but their small size prevents detection by standard light microscopy.
• Current methods lack a fast, simple way to identify pili on live single bacterial cells.

Purpose of the Study:

• To develop a novel, rapid, and non-destructive method for detecting adhesion pili on individual bacterial cells.
• To enable real-time differentiation between piliated and non-piliated bacteria for subsequent live-cell studies.

Main Methods:

• Imaging bacteria to measure cell size and predict fluid drag using an analytical model.
• Trapping single bacteria with optical tweezers and oscillating the sample to measure effective fluid drag.
• Comparing predicted fluid drag with measured fluid drag to infer the presence of pili.

Main Results:

• The method successfully detected the presence of pili by comparing predicted and measured fluid drag.
• Verified the protocol using polymer-coated silica microspheres and Escherichia coli expressing adhesion pili.
• Demonstrated real-time, within-seconds capability to distinguish piliated from non-piliated bacteria.

Conclusions:

• This optical tweezer-based fluid drag measurement offers a fast and simple approach to identify pili on single bacterial cells.
• The developed protocol supports live-cell studies by enabling rapid identification of piliated bacteria.
• This technique advances the study of bacterial adhesion, biofilm formation, and infection dynamics.