A Biosensor for Detection of Indole Metabolites

Microbially produced indole metabolites
serve as a diverse family
of interspecies and interkingdom signaling molecules in the context
of human health, crop production, and antibiotic resistance. We mined
the protein database for sensors of indole metabolites and developed
a biosensor for indole-3-aldehyde (I3A). Microbially produced I3A
has been associated with reducing inflammation in diseases such as
ulcerative colitis by stimulating the aryl hydrocarbon receptor pathway.
We engineered an E. coli strain embedded with
a single plasmid carrying a chimeric two-component system that detects
I3A. Our I3A receptor characterization confirmed binding site residues
that contribute to the sensor’s I3A detection range of 0.1–10
μM. This new I3A biosensor opens the door to sensing indole
metabolites produced at various host–microbe interfaces and
provides new parts for synthetic biology applications.