Directing microbial co-culture composition using cybernetic control.

Area of Science:

• Synthetic Biology
• Biotechnology
• Control Engineering

Background:

• Microbial co-cultures are essential in biotechnology but challenging to control.
• Existing methods often rely on genetic engineering, limiting broad applicability.
• Precise, non-invasive control strategies are needed for stable co-culture management.

Purpose of the Study:

• To develop and demonstrate a cybernetic framework for controlling the composition of a bacterial co-culture (Pseudomonas putida and Escherichia coli).
• To achieve this control without employing genetic engineering for cell-computer interfacing.
• To establish a broadly applicable method for robustly managing diverse microbial consortia.

Main Methods:

• Utilized bioreactor measurements to extract real-time composition information.
• Integrated measurements with a system model using an extended Kalman filter for accurate state estimation.
• Employed temperature as a control input, leveraging differential species' optimal growth temperatures.
• Implemented a proportional-integral (PI) control algorithm for dynamic reference tracking and noise rejection.

Main Results:

• Successfully estimated co-culture composition from noisy bioreactor data.
• Demonstrated temperature-driven control of microbial composition.
• Achieved stable co-culture maintenance for 7 days (approximately 250 generations) using PI control.
• Showcased independence from initial inoculation ratios and effective real-time noise rejection.

Conclusions:

• The developed cybernetic framework enables precise, non-genetic control of microbial co-cultures.
• This approach offers a robust and broadly applicable strategy for managing microbial consortia in synthetic biology and biotechnology.
• The method successfully stabilized a P. putida and E. coli co-culture, demonstrating its practical viability.