The Iron‐responsive, Uropathogenic E.coli Exometabolome Is Dominated by Multiple Enterobactin‐derived Catechols

Abstract

Uropathogenic E. coli possess numerous iron‐responsive genes that are transcriptionally upregulated during human and experimental cystitis. These gene products are involved in diverse functions, including transporters and biosynthesis of specialized metabolites with virulence‐associated functions. Here, we sought to identify iron‐responsive exometabolites in experimental cultures of the model uropathogenic E. coli strain UTI89. Using comparative metabolomics, we detected multiple iron‐regulated products related to the siderophore enterobactin. In addition to observing the canonical siderophores enterobactin and salmochelin, we also detected siderophore structurally related, lower molecular weight metabolites of unknown origins. We considered that these low molecular weight products may derive from premature release from the biosynthetic complex (anabolic products) or from degradation of the full siderophore (catabolic products). In siderophore import‐deficient UTI89ΔtonB, low molecular weight catechols were substantially attenuated, in particular for the glucosylated derivatives, which favors a catabolic source of low molecular weight catechols resulting from import and incomplete hydrolysis of ferric enterobactin and salmochelin. When siderophore biosynthetic mutants were cultured with purified enterobactin, enterobactin was consumed while low molecular weight catechol products were not generated. And isotope‐labelling experiments suggest that complete enterobactin hydrolysis products may be recycled by bacteria within the cells for subsequent rounds of enterobactin biosynthesis. The results then raise a new hypothesis of glucosylation resulting in different enterobactin and salmochelin catabolisms, which is currently being investigated. The secreted exometabolome of uropathogenic E. coli includes not only siderophores but siderophore‐related products that arise from transport, hydrolytic, and recycling pathways that may relate to these organisms’ pathogenic potential.Support or Funding InformationAcknowledgements:This work was supported by a CDC Prevention Epicenters Program Grant CU54CK000162 and National Institutes of Health R01DK099534 and R01DK111930 to JPH.