Engineering a chimeric malate two-component system by introducing a positive feedback loop in Escherichia coli

Previous studies constructed a chimeric MalKZ two-component system to sense environmental malate. In this study, we used a positive feedback loop to accelerate and amplify the output signal indicating malate concentration. The positive feedback loop was constructed by cloning ompR gene, which encodes ompC and induces OmpR protein; ompC promoter was used to control the process. The transcriptional expression profile showed that the expression level of ompC gene increased about two-fold after the positive feedback loop was introduced. When GFP was used as a reporter protein, a 71% increase in fluorescence level was observed. The results indicate that the signal transduction kinetics of MalKZ can be engineered by introducing the positive feedback loop.