Enterobacteria secrete an inhibitor of Pseudomonas virulence during clinical bacteriuria
Shannon I. Ohlemacher, Daryl E. Giblin, D. André d’Avignon, Ann E. Stapleton, Barbara W. Trautner, Jeffrey P. Henderson
Shannon I. Ohlemacher, Daryl E. Giblin, D. André d’Avignon, Ann E. Stapleton, Barbara W. Trautner, Jeffrey P. Henderson
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Research Article Infectious disease

Enterobacteria secrete an inhibitor of Pseudomonas virulence during clinical bacteriuria

Abstract

Escherichia coli and other Enterobacteriaceae are among the most common pathogens of the human urinary tract. Among the genetic gains of function associated with urinary E. coli isolates is the Yersinia high pathogenicity island (HPI), which directs the biosynthesis of yersiniabactin (Ybt), a virulence-associated metallophore. Using a metabolomics approach, we found that E. coli and other Enterobacteriaceae expressing the Yersinia HPI also secrete escherichelin, a second metallophore whose chemical structure matches a known synthetic inhibitor of the virulence-associated pyochelin siderophore system in Pseudomonas aeruginosa. We detected escherichelin during clinical E. coli urinary tract infection (UTI) and experimental human colonization with a commensal, potentially probiotic E. coli bacteriuria strain. Escherichelin production by colonizing enterobacteria may help human hosts resist opportunistic infections by Pseudomonas and other pyochelin-expressing bacteria. This siderophore-based mechanism of microbial antagonism may be one of many elements contributing to the protective effects of the human microbiome. Future UTI-preventive probiotic strains may benefit by retaining the escherichelin biosynthetic capacity of the Yersinia HPI while eliminating the Ybt biosynthetic capacity.

Authors

Shannon I. Ohlemacher, Daryl E. Giblin, D. André d’Avignon, Ann E. Stapleton, Barbara W. Trautner, Jeffrey P. Henderson

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Figure 3

Identification of escherichelin as HPTT-COOH, a metallophore inhibitor of Pseudomonas iron uptake.

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Identification of escherichelin as HPTT-COOH, a metallophore inhibitor o...
(A) Multiple chemical characterizations identify escherichelin as HPTT-COOH, a compound shown to inhibit pyochelin-mediated iron uptake in Pseudomonas. The positions of 13C salicylate incorporation are indicated in green, while MS/MS neutral losses are indicated as dashed lines. (B) Mass spectra at the retention time for escherichelin from WT UTI89, UTI89ΔybtS, and 13C6-SA–supplemented UTI89ΔybtS culture supernatants revealed that 6 carbons in escherichelin are derived from salicylate. (C) MS/MS product ion spectrum of escherichelin. The 46-Da neutral loss indicates the presence of a carboxylic acid group, and the 87- and 104-Da losses correspond to fragmentation within the thiazoline ring. (D) UV-visible absorption spectra of purified escherichelin incubated with equimolar FeCl3 or CuSO4. (E and F) DFT simulations of escherichelin bound to Fe(III) in a 1:1 (E) and 2:1 (F) complex. The simulations predict stable Fe(III)-escherichelin complexes with hexacoordinate octahedral geometry. (G) UTI89 growth curve in the presence or absence of a ferric ion chelator (0.5 mM EDDHA) and/or ferric ion supplementation (1 μM FeCl3). Growth was monitored by OD at 600 nm (OD600). Data represent the mean of 3, with SD plotted. (H) PW5011 (pvdA-E02::ISlacZ/hah), a P. aeruginosa strain MPAO1 transposon mutant (55, 56) expressing pyochelin as its sole siderophore, was grown in succinate medium for 20 hours in the presence of increasing escherichelin concentrations relative to vehicle control. Bacterial growth was quantified by enumerating CFU/ml and is expressed as a percentage of the vehicle control. Data represent the mean of 3, with the SEM plotted. *P < 0.01 and **P < 0.001, by 1-way ANOVA with Dunnett’s multiple comparisons test.