Fig. 6: The iron-limiting conditions induced by entacapone select for siderophore producers and drive an increase in AMR and virulence potential in the faecal microbiome.

a, Genetic organization of the enterobactin biosynthesis locus in E. coli D bin.187. Genes encoding enzymes involved in enterobactin biosynthesis (entABCDEFH) and export (entS) are highlighted in orange. The steps of enterobactin synthesis catalysed by the products of these genes are shown at the bottom. Genes involved in enterobactin import and iron release are highlighted in blue. b, Growth of the E. coli isolate E2, highly identical to E. coli D bin.187 determined by optical density measurements of cultures supplemented or not with entacapone (ENT-Hi) and/or FeSO₄ (Fe). Data represent the mean ± s.e.m. of 3 independent growths. c, Growth of E. coli K12 BW25113 wild-type (wt), entB (ΔentB) or fepA (ΔfepA) mutants determined by optical density measurements of cultures supplemented or not with ENT-Hi and/or enterobactin. Data represent the mean ± s.e.m. of 3 independent growths (Supplementary Table 19). *P < 0.05, **P < 0.01; ***P < 0.001; unpaired two-sided t-test with ‘E. coli wt’ used as the reference. d, Schematic representation of the working hypothesis. In the absence of entacapone (left), enough iron is available to most gut microbiome members. Under ENT-Hi conditions, entacapone complexes available iron (ENT:Fe), and only organisms able to produce and/or import siderophores (represented by diamonds) for iron scavenging are able to grow and thrive (right). Created with Biorender.com. e, Increase in the AMR and virulence index (Methods) in no drug controls and entacapone (ENT-Hi)-treated samples. Boxes represent the median, first and third quartiles. Whiskers extend to the highest and lowest values that are within 1.5× the interquartile range. Indicated P values were obtained from unpaired two-sided t-test comparing the groups ‘Ent-Hi’ and ‘No drug’ at each indicated timepoint.