Trajectory analysis of Bacillus subtilis in micro-droplets

Area of Science:

• Microbiology
• Biophysics
• Bioengineering

Background:

• Biofilm formation is crucial for bacterial survival and pathogenesis.
• Understanding bacterial behavior in confined environments like microdroplets is key to controlling biofilm development.
• Bacillus subtilis is a model organism for studying biofilm formation.

Purpose of the Study:

• To investigate the spatial distribution and motility patterns of Bacillus subtilis during biofilm formation in microdroplets.
• To develop and apply advanced imaging and tracking techniques for analyzing bacterial behavior at the single-cell level.
• To correlate bacterial motility and spatial location with biofilm development within microdroplets.

Main Methods:

• Microfluidics was used to generate and maintain stable microdroplets for bacterial culture.
• Confocal microscopy enabled real-time visualization of bacterial cells and biofilm structures.
• A multi-target tracking methodology, integrating YOLOv5 and DeepSORT algorithms, was employed to quantify cell movement.

Main Results:

• Bacillus subtilis cells preferentially aggregated and swarmed near the microdroplet surface, not the interior.
• Motile cells exhibited significantly higher speeds (3.5x) compared to matrix-producing cells.
• Motile cell movement was directed along the droplet wall when near the surface, but disordered in the droplet interior.

Conclusions:

• The distinct motility patterns of Bacillus subtilis near the microdroplet surface enhance cell-cell contact probability, promoting biofilm formation.
• Spatial localization and differential motility are critical factors influencing Bacillus subtilis biofilm development in microdroplets.
• The developed mathematical model provides insights into the role of motility in microdroplet biofilm dynamics.