A Recombinase-Based Genetic Circuit for Heavy Metal Monitoring

Abstract

Rapid progress in the genetic circuit design enabled whole-cell biosensors (WCBs) to become prominent in detecting an extensive range of analytes with promise in many fields, from medical diagnostics to environmental toxicity assessment. However, several drawbacks, such as high background signal or low precision, limit WCBs to transfer from proof-of-concept studies to real-world applications, particularly for heavy metal toxicity monitoring. For an alternative WCB module design, we utilized Bxb1 recombinase that provides tight control as a switch to increase dose-response behavior concerning leakiness. The modularity of Bxb1 recombinase recognition elements allowed us to combine an engineered semi-specific heat shock response (HSR) promoter, sensitive to stress conditions including toxic ions such as cadmium, with cadmium resistance regulatory elements; a cadmium-responsive transcription factor and its cognitive promoter. We optimized the conditions for the recombinase-based cadmium biosensor to obtain increased fold change and shorter response time. This system can be expanded for various heavy metals to make an all-in-one type of WCB, even using semi-specific parts of a sensing system.

Applications of Serine Integrases in Synthetic Biology over the Past Decade

“…Input signals enable cells to sense and respond the external environment for altering their metabolism and behavior (Figure 8, middle left). Up to now, the main inducers for serine integrase expression are chemical molecules [43] such as arabinose, anhydrotetracycline, 2,4-diacetylphloroglucinol (DAPG), and some metal ions like cadmium [93] with strictly regulated inducible circuits to prohibit leakage. In addition, some studies showed other physical factor-induced serine (or tyrosine) integrase-manipulated genetic circuits.…”

Engineering of a Bacterial Biosensor for the Detection of Chlorate in Food

“…Synthetic biology has made it possible to genetically engineer bacteria and create bacterial biosensors that can detect a specific molecule or chemical through intrinsic regulatory mechanisms. Typically, these biosensors involve a sensing module and a reporting module that generates a readily detectable output signal [ 23 , 24 , 25 ]. For the chlorate biosensor we present in this study, we used the bacteria Escherichia coli .…”

A review of biosensor for environmental monitoring: principle, application, and corresponding achievement of sustainable development goals

“…Recent studies have applied both recA -based and metabolic inhibition-based bioluminescence bacterial biosensor for pollutants such as toxic metals in urban rivers and seawater [ 70 , 71 ]. Similarly, the stress-inducible heat shock genes like hsp70 and its promoter were used in biosensors for detecting nonspecific toxicity since the heat shock protein systems will be triggered not only by heat shock but also other environmental stressors, and then induce the downstream fused signals [ 72 , 73 ].…”