Design

Three Designed Devices to Achieve Our Goals

1. PFAS-sensitive Promoter (prmA) Device: The expression of subsequent elements is driven by the PFAS-sensitive promoter prmA. When the PFAS concentration in the environment is high, the prmA promoter is activated, initiating the expression of the dhaA gene (which encodes PFAS dehalogenase) and the gene encoding GFP (Green Fluorescent Protein) simultaneously. This causes the engineered bacteria to emit green fluorescence under excitation light. In the absence of PFAS in the environment, the downstream genes remain unexpressed.
   
2. Fluoride Ion-activated Transporter Device: The fluoride ion transporter, F¯ riboswitch, and the transcriptional product of this gene are located on the same mRNA. When no F¯ are bound, the F¯ riboswitch forms a hairpin structure, blocking the translation process. When F¯ are present in the environment, the small molecules bind to the conserved stem-loop region, thereby mediating the unfolding of the hairpin structure, then activating the expression of the F¯ transporter CrcB. This reduces the intracellular F¯ concentration, ensuring the bacteria can survive normally even under relatively high F¯ concentrations. Meanwhile, the expression of mCherry protein is initiated, enabling real-time monitoring of PFAS degradation by the engineered bacteria.
   
3. Arabinose Operon-regulated ccdB Suicide Device: This Device significantly enhances the safety of our engineered bacteria. In the absence of arabinose, the AraC protein (expressed by the araC gene) binds to DNA, thereby inhibiting the expression of the ccdB gene. When the arabinose concentration in the environment is low, the expression of the ccdB gene remains repressed. As the arabinose concentration increases, arabinose binds to the AraC protein, activating the pBAD promoter and thus promoting the expression of the ccdB gene, ultimately achieving bacterial self-destruction.