University of Dundee

MRC DTP: The role of multidrug efflux pumps in Gram-negative drug resistance and bacterial persistence

The majority of drug-resistant “priority pathogens”, as defined by the World Health Organization (WHO), are Gram-negative bacteria [1]. These organisms have evolved critical resistance against the presently available arsenal of antibiotics, while almost no new drug candidates with Gram-negative activity are under development. The cell envelope of Gram-negative bacteria poses a formidable barrier to drug permeation, and it is exceptionally difficult to achieve broad-spectrum drug activity with the current strategies of drug design.

One of the most important contributors to insufficient drug permeation and expulsion, underpinning drug resistance, is the action of tripartite efflux pumps [2]. In this project, we will focus on the function of MexAB-OprM, the major tripartite efflux pump of Pseudomonas aeruginosa, an important opportunistic pathogen that causes 10–15% of all hospital infections worldwide with a mortality rate of up to 61%. Efflux pumps can remain active and contribute to antibiotic tolerance even in states of low metabolic activity, such as those occupied by “persisters” [3].

We will use a combination of biomolecular simulations, microbiology experiments, and machine learning on drug permeation data to

  • better understand the molecular-level mechanism of efflux through the MexAB-OprM complex and its coupling to proton gradients as cellular energy source;
  • find routes towards inhibiting the efflux pump mechanism;
  • experimentally elucidate the role of MexAB-OprM in drug resistance and the evolution of P. aeruginosa persister cells
  • identify molecular features that determine whether a drug is effluxed or not.

[1] Tacconelli et al., The Lancet Infectious Diseases, 2018; doi: 10.1016/S1473-3099(17)30753-3

[2] e.g., Fitzpatrick et al., Nature Microbiol. 2017; doi: 10.1038/nmicrobiol.2017.70

[3] Pu et al., Molecular Cell. 2016; doi: 10.1016/j.molcel.2016.03.035

Recent work from the lab can be found in the following references: 


  • Kopec et al., Nature Chemistry, 2018; doi: 10.1038/s41557-018-0105-9
  • Alghamdi et al., eLife, 2020; doi: 10.7554/elife.56416.sa2
  • Williamson et al., eLife, 2020; doi: 10.7554/eLife.57183


  • Meirelles et al., bioRxiv, 2020; doi: 10.1101/2020.04.20.049437
  • Bergkessel, Current Opinion Microbiology, 2020; doi: 10.1016/j.mib.2020.07.010
  • Bergkessel et al., Molecular Microbiology, 2019; doi: 10.1111/mmi.14337