Engineering Transcription Factor-Based Biosensors for the Detection of Intracellular Products

Abstract

The screening of novel enzymes and efficient production strains for the production of small molecules becomes more and more important for fast and reliable strain construction. Increased concentrations of small molecules often do not lead to a measurable phenotype, which impedes rapid detection of improved production strains. Metabolite biosensors based on transcription factors are currently an upcoming method for detection of intracellular metabolites in vivo. This technique couples the response of a transcription factor to the readout of a fluorescent reporter protein. The described example is based on the transcriptional repressor QdoR from Bacillus subtilis, which is inactivated by some flavonoids (e.g., kaempferol). The constructed biosensor showed over sevenfold increase of the fluorescent signal after addition of the effector and was successfully applied for detection of kaempferol production in vivo in Escherichia coli cells containing a flavonol synthase from Arabidopsis thaliana (fls1).