Metabolomics Reveal Potential Natural Substrates of AcrB in <i>Escherichia coli</i> and <i>Salmonella enterica</i> Serovar Typhimurium

Xuan, Wang-Kan, Rodriguez-Blanco, Giovanny, Southam, Andrew D, Winder, Catherine L, Dunn, Warwick B ORCID: 0000-0001-6924-0027, Ivens, Alasdair and Piddocka, Laura JV
(2021) Metabolomics Reveal Potential Natural Substrates of AcrB in <i>Escherichia coli</i> and <i>Salmonella enterica</i> Serovar Typhimurium. MBIO, 12 (2). e00109-e00121.

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In the fight against antibiotic resistance, drugs that target resistance mechanisms in bacteria can be used to restore the therapeutic effectiveness of antibiotics. The multidrug resistance efflux complex AcrAB-TolC is the most clinically relevant efflux pump in <i>Enterobacterales</i> and is a target for drug discovery. Inhibition of the pump protein AcrB allows the intracellular accumulation of a wide variety of antibiotics, effectively restoring their therapeutic potency. To facilitate the development of AcrB efflux inhibitors, it is desirable to discover the native substrates of the pump, as these could be chemically modified to become inhibitors. We analyzed the native substrate profile of AcrB in <i>Escherichia coli</i> MG1655 and <i>Salmonella enterica</i> serovar Typhimurium SL1344 using an untargeted metabolomics approach. We analyzed the endo- and exometabolome of the wild-type strain and their respective AcrB loss-of-function mutants (AcrB D408A) to determine the metabolites that are native substrates of AcrB. Although there is 95% homology between the AcrB proteins of <i>S.</i> Typhimurium and <i>E. coli</i>, we observed mostly different metabolic responses in the exometabolomes of the <i>S.</i> Typhimurium and <i>E. coli</i> AcrB D408A mutants relative to those in the wild type, potentially indicating a differential metabolic adaptation to the same mutation in these two species. Additionally, we uncovered metabolite classes that could be involved in virulence of <i>S.</i> Typhimurium and a potential natural substrate of AcrB common to both species.<b>IMPORTANCE</b> Multidrug-resistant Gram-negative bacteria pose a global threat to human health. The AcrB efflux pump confers inherent and evolved drug resistance to <i>Enterobacterales</i>, including <i>Escherichia coli</i> and <i>Salmonella enterica</i> serovar Typhimurium. We provide insights into the physiological role of AcrB: (i) we observe that loss of AcrB function in two highly related species, <i>E. coli</i> and <i>S.</i> Typhimurium, has different biological effects despite AcrB conferring drug resistance to the same groups of antibiotics in both species, and (ii) we identify potential natural substrates of AcrB, some of which are in metabolite classes implicated in the virulence of <i>S.</i> Typhimurium. Molecules that inhibit multidrug efflux potentiate the activity of old, licensed, and new antibiotics. The additional significance of our research is in providing data about the identity of potential natural substrates of AcrB in both species. Data on these will facilitate the discovery of, and/or could be chemically modified to become, new efflux inhibitors.

Item Type: Article
Uncontrolled Keywords: AcrAB, AcrAB-TolC, physiological substrates, efflux, Enterobacterales, Escherichia coli, Salmonella, drug efflux, efflux pumps
Divisions: Faculty of Health and Life Sciences
Faculty of Health and Life Sciences > Institute of Systems, Molecular and Integrative Biology
Depositing User: Symplectic Admin
Date Deposited: 17 Jan 2022 10:15
Last Modified: 05 Oct 2023 11:35
DOI: 10.1128/mBio.00109-21
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