Design and Optimization\nof a Two-Component TorRST-Based\nBiosensor for Detection and Degradation of Trimethylamine N‑Oxide

In mammals, Trimethylamine N-oxide (TMAO) is involved\nin various\nphysiological processes, and is considered a biomarker for multiple\ndiseases. As a natural molecule found in marine organisms, TMAO is\nalso an important indicator of seafood freshness. In this study, a\nTMAO biosensor was developed in Escherichia coli harnessing TorRST two-component system. By using a cascade amplification\ncircuit based on HrpRS-P<i><sub>hrpL</sub></i>, the biosensor’s\ndynamic range was increased from 4.1- to 10.3-fold. By optimizing\nthe affinity between the regulatory protein TorR and DNA binding sites\nin promoters, the concentration for 50% of maximal effect (EC<sub>50</sub>) value was reduced from 1008 to 141 μM. The biosensor\nwas successfully used for aquatic sample detection. By introducing\nan exogenous TMAO degradation pathway into E. coli Nissle 1917, a probiotic chassis capable of TMAO detection, transportation,\nand degradation was constructed, providing an effective tool for rapid\ndetection of TMAO and prevention of multiple diseases.