Synthetic Cassettes for pH-Mediated Sensing, Counting, and Containment

Area of Science:

• Synthetic Biology
• Microbial Engineering
• Genetic Circuit Design

Background:

• pH is critical for biological processes, necessitating precise environmental sensing.
• Unintentional release of engineered bacteria raises safety concerns.
• Genetic circuits offer potential for bacterial containment and control.

Purpose of the Study:

• To develop a robust pH-sensitive bacterial kill switch for enhanced biological containment.
• To engineer a multi-factor containment system combining pH sensing with other control mechanisms.
• To create advanced genetic circuits for precise bacterial population management.

Main Methods:

• Utilized the Escherichia coli asr promoter to create the pH-sensitive kill switch (acidTRP).
• Integrated acidTRP with a cryodeath system to establish a two-factor containment strategy.
• Developed a pulse-counting circuit with single-cell readout for stimulus response tracking.

Main Results:

• Achieved a survival ratio of <1 in 10^6 with the acidTRP system.
• Demonstrated a combined survival ratio of <1 in 10^11 with the two-factor acidTRP and cryodeath system.
• Successfully implemented a 2-count acid-sensitive kill switch capable of recording multiple pH changes.

Conclusions:

• Engineered genetic systems can provide effective and evolutionary stable biological containment.
• Complex genetic circuits, including pH sensing and pulse counting, can be reliably constructed.
• This work advances the development of sophisticated tools for microbial safety and control.