Single bacteria movement tracking by online microscopy--a proof of concept study

Area of Science:

• Microbiology
• Biotechnology
• Process Engineering

Background:

• Monitoring bacterial metabolic states (viability) is crucial for optimizing fermentation processes.
• Existing methods for viability assessment can be limited, especially in turbid media.
• Single-cell movement analysis offers a potential alternative for real-time viability assessment.

Purpose of the Study:

• To develop and validate a low-cost online system for tracking flagellated bacteria at the single-cell level during fermentation.
• To investigate the correlation between bacterial movement velocity and metabolic state (viability).
• To assess the system's utility as a bacteria viability monitoring tool in production settings.

Main Methods:

• Development of a flow-through cuvette with adjustable layer thickness compatible with standard laboratory microscopes.
• Creation of an automated sample preparation unit and software for measuring bacterial size, distance, and speed.
• Application of the system to monitor movement velocities of Bacillus amyloliquefaciens FZB42 during batch fermentation.

Main Results:

• The developed system successfully tracked individual bacteria and measured their movement parameters.
• Significant differences in movement velocities were observed between distinct metabolic states (vegetative growth, diauxic shift, sporulation).
• The system demonstrated the ability to distinguish between different bacterial metabolic states based on movement velocity.

Conclusions:

• The developed low-cost online unit is a promising tool for monitoring bacterial viability during fermentation based on single-cell movement analysis.
• The system's ability to function in turbid media offers an advantage over other techniques like electro-optical methods.
• This approach provides a novel, non-invasive method for real-time assessment of bacterial metabolic status in industrial bioprocesses.