In the field of synthetic biology, biosafety has always been the cornerstone of a project’s success. Any genetic engineering design intended for real-world application must be based on rigorous safety measures.In our project, we focus on engineering E. coli to degrade residual chlorimuron-ethyl, a commonly used herbicide in soybean fields.
Our goal is twofold — to use engineered bacteria to remove herbicide residues while secreting indole-3-acetic acid (IAA) to promote crop germination, and to introduce a cold-inducible suicide system to ensure environmental safety. Therefore, biosafety measures are not only laboratory regulations, but also the key assurance that our engineered bacteria remain “useful yet harmless” throughout research, testing, and application.
Chlorimuron-ethyl Risk Assessment
Chlorimuron-ethyl is a selective sulfonylurea herbicide that effectively controls broadleaf weeds in soybean fields.
However, long-term or improper use can lead to multiple risks:
- Soil Ecological Risk – Chlorimuron-ethyl has a long half-life in soil, allowing accumulation that disrupts soil microbial communities, leading to soil degradation.
- Crop Phytotoxicity – Due to persistent residues, it can cause chemical injury to subsequent crops such as wheat, maize, and rice, resulting in reduced germination, leaf chlorosis, and root malformation, ultimately lowering yields and disrupting crop rotation systems.
- Water and Ecological Risk – When washed into water bodies via runoff, it exhibits toxicity to algae, plankton, and aquatic organisms, disturbing the aquatic ecosystem balance.
- Potential Health Risk – Although its acute toxicity is low, long-term exposure or bioaccumulation through the food chain may pose chronic health risks.
Engineered Bacteria Risk Statement
If engineered bacteria survive long-term in the natural environment, there is a potential risk of horizontal gene transfer to native soil microbes. Additionally, release of genetically modified microorganisms (GMMs) could raise public concern among farmers and consumers regarding biosafety.
Suicide System
A cold-inducible promoter (PcspA) drives the expression of T4 holin, which triggers cell lysis when the ambient temperature decreases, preventing overproliferation of engineered bacteria in the environment.
Laboratory-limited Use
All experiments are conducted strictly within a controlled laboratory environment, and no field trials are performed.
Modular Design:
The chlorimuron-ethyl degradation module, IAA synthesis module, and suicide module are independently verified, ensuring system controllability and safety.
Personal Protection
- Laboratory personnel must wear lab coats, gloves, and protective goggles during all experiments.
- All bacterial culture and media handling are performed under a biosafety cabinet to prevent cross-contamination.
- Waste cultures and media are autoclaved before disposal to eliminate biological hazards.
Safety Training
- All team members are required to complete biosafety training, covering biosafety levels, chemical management, and emergency response.
- Experiments such as molecular cloning, transformation, and cultivation are performed under the supervision of instructors.
- Regular safety drills are conducted to practice bioleakage response and accident management.
Laboratory Safety Regulations
Clear safety regulations are established for all laboratory areas. As shown in the figure, there are two categories of rules: Electrophoresis area safety guidelines, and General laboratory operation safety guidelines. All personnel entering the laboratory must study and strictly comply with these rules to ensure both experimental integrity and personal safety.
