A FRET-based color-changing whole-cell biosensor for visual detection of 2,4-dinitrotoluene

BL21(DE3) to construct the biosensor. In the absence of 2,4-DNT, the cells exhibited yellow fluorescence due to FRET between mAmetrine and TagRFP. In the presence of 2,4-DNT, expression of TVMV protease cleaved the linker peptide, disrupted FRET, and resulted in green fluorescence. A clear fluorescence color change from yellow to green was observed in response to 0-1 mM 2,4-DNT. Cleavage of the linker peptide by TVMV protease was confirmed by SDS-PAGE. These results demonstrate the feasibility of a color-changing microbial biosensor for visual detection of 2,4-DNT. This strategy provides a visual output independent of signal intensity.