Abstract:
Enteropathogenic Escherichia coli (EPEC), enterohemorrhagic E. coli (EHEC) and enteroaggregative E. coli (EAEC) are
intestinal pathogens that cause food and water-borne disease in humans. Using biochemical methods and NMR-based
comparative metabolomics in conjunction with the nematode Caenorhabditis elegans, we developed a bioassay to identify
secreted small molecules produced by these pathogens. We identified indole, indole-3-carboxaldehyde (ICA), and indole-3-
acetic acid (IAA), as factors that only in combination are sufficient to kill C. elegans. Importantly, although lethal to C. elegans,
these molecules downregulate several bacterial processes important for pathogenesis in mammals. These include motility,
biofilm formation and production of Shiga toxins. Some pathogenic E. coli strains are known to contain a Locus of
Enterocyte Effacement (LEE), which encodes virulence factors that cause ‘‘attaching and effacing’’ (A/E) lesions in mammals,
including formation of actin pedestals. We found that these indole derivatives also downregulate production of LEE
virulence factors and inhibit pedestal formation on mammalian cells. Finally, upon oral administration, ICA inhibited
virulence and promoted survival in a lethal mouse infection model. In summary, the C. elegans model in conjunction with
metabolomics has facilitated identification of a family of indole derivatives that broadly regulate physiology in E. coli, and
virulence in pathogenic strains. These molecules may enable development of new therapeutics that interfere with bacterial
small-molecule signaling.
