A pH-responsive genetic sensor for the dynamic regulation of D-xylonic acid accumulation in Escherichia coli

A pH-responsive genetic sensor for the dynamic regulation of D-xylonic acid accumulation in Escherichia coli:

Abstract

The xylose oxidative pathway (XOP) is continuously gaining prominence as an alternative for the traditional pentose assimilative pathways in prokaryotes. It begins with the oxidation of D-xylose to D-xylonic acid, which is further converted to α-ketoglutarate or pyruvate + glycolaldehyde through a series of enzyme reactions. The persistent drawback of XOP is the accumulation of D-xylonic acid intermediate that causes culture media acidification. This study addresses this issue through the development of a novel pH-responsive synthetic genetic controller that uses a modified transmembrane transcription factor called CadCΔ. This genetic circuit was tested for its ability to detect extracellular pH and to control the buildup of D-xylonic acid in the culture media. Results showed that the pH-responsive genetic sensor confers dynamic regulation of D-xylonic acid accumulation, which adjusts with the perturbation of culture media pH. This is the first report demonstrating the use of a pH-responsive transmembrane transcription factor as a transducer in a synthetic genetic circuit that was designed for XOP. This may serve as a benchmark for the development of other genetic controllers for similar pathways that involve acidic intermediates.