Effect of ethanolamine utilization on the pathogenicity and metabolic profile of enterotoxigenic Escherichia coli

Bacterial pathogenicity is greatly affected by nutrient recognition and utilization in the host microenvironment. The characterization of enteral nutrients that promote intestinal pathogen virulence is helpful for developing new adjuvant therapies and inhibiting host damage. Ethanolamine (EA), as a major component of intestinal epithelial cells and bacterial membranes, is abundant in the intestine. Here, we provide the first demonstration that the critical human and porcine pathogen enterotoxigenic Escherichia coli (ETEC) can utilize EA as a nitrogen source, which affects its virulence phenotype. We found that compared with that in M9 medium (containing NH₄Cl), EA inhibited ETEC growth to a certain extent; however, the relative expression levels of virulence-related genes, such as ltA (3.0-fold), fimH (2.9-fold), CfaD (2.6-fold), gspD (3.6-fold), and qesE (1.3-fold), increased significantly with 15 mM EA as a nitrogen source (P < 0.05), and the adhesion efficiency of ETEC to Caco-2 cells increased approximately 4.2-fold. In Caco-2 cells, the relative cell viability decreased from 74.8 to 63.4%, and the transepithelial electrical resistance (TEER) cells decreased to 74.8% with intestinal EA (4 mM). In addition, the relative expression levels of proinflammatory factors, such as TNF-α (3.2-fold), INF-γ (2.9-fold), and IL-1β (1.98-fold), in ETEC-infected Caco-2 cells were significantly upregulated (P < 0.05) under EA exposure; however, the above virulence changes were not found in ΔeutR and ΔeutB ETEC. A gas chromatography-mass spectrometry (GC-MS)-based untargeted metabolomics approach was then employed to reveal EA-induced metabolic reprogramming related to ETEC virulence. The data showed that most metabolites related to carbohydrate, aspartate and glutamate metabolism, shikimic acid metabolism, and serine metabolism in ETEC exhibited a decreasing trend with increases in the EA concentration from 0 to 15 mM, but the branched-chain amino acid (BCAA) levels in ETEC increased in a dose-dependent manner under EA exposure. Our data suggest that the intestinal EA concentration can significantly affect the virulence phenotype, metabolic profile, and pathogenicity of ETEC. KEY POINTS: • ETEC growth and virulence gene expression could be regulated by ethanolamine. • The intestinal concentration of EA promoted the damaging effect of ETEC on the host epithelial barrier. • The promoting effect of EA on ETEC toxicity may be related to BCAA metabolism.