(710c) Modulation of Chemotaxis By an Interkingdom Signaling Molecule

The mammalian gastrointestinal (GI) tract harbors a diverse community of microbes, collectively known as the microbiota. Metabolites produced by the GI tract microbiota are known to be key regulators of disease and infections. In particular, Indole has received wide attention for its role as an intercellular, interspecies and interkingdom signaling molecule. Indole is a known regulator of a variety of bacterial responses, including biofilm formation and virulence. Of particular interest is its ability to regulate bacterial chemotaxis and motility, with implications for surface colonization and infections. However, the mechanisms of control are unknown. Here, we dissected these mechanisms in E. coli. I will discuss our combined use of perfusion assays, Förster resonance energy transfer (FRET) measurements, and single flagellar motor assays to map out the precise chemotactic modules that are influenced by Indole. We see strong evidence of competing interactions between two major chemoreceptor types, which mediate a temporal inversion in the chemotactic response to Indole. Contrary to recent claims, Indole does not appear to modulate the proton motive force, nor does it impact the cytoplasmic pH, appreciably. I will discuss a modular analytical model which correctly predicts the experimental data. Our work provides fundamental insights regarding Indole-based modulation of chemotaxis and motility, and paves the way for future studies on combinatorial regulation of chemotaxis by metabolites.