Engineering Synthetic Stress-responsive Elements for Detection of Various Types of Cellular Damage

Synthetic biology aims to reprogram living cells to control signal processing for redirected, practicable applications. Here we demonstrate the design and fabrication of bacterial biosensors in Escherichia coli implementing various engineering concepts adapted from synthetic biology. Various whole-cell bacterial strains have been genetically engineered to detect a broad spectrum of toxicity including DNA damage, membrane damage, protein damage, oxidative stress, organic toxins, and heavy metals. To date, the main guideline in whole-cell biosensors engineering has mainly based on single-input, encompassing a promoter which senses the presence of the toxin followed and activated by a second unit, which is downstream reporting gene. However, such concept has greatly failed to deal with real-world samples which require higher computational complexity, low detection threshold, specificity and stability. In this work, the whole-cell biosensors were constructed using native stress-responsive elements extracted from Escherichia coli genome and further combined with synthetic regulators for improvement of bacterial biosensors. In bacterial stress biosensors, each stress response activates a different complex cascades of proteins embedded in broad and global regulatory circuits. To improve the biosensor ON/OFF activity and to reduce its basal level we used TI mechanism (Transcriptional interference) which occurs when transcription from one promoter on sense strand interferes with transcription from adjacent promoter on the anti-sense strand.